I just made this map, (6 Jan 2000) and I haven't come-up with the full descriptions of the cities and towns yet. What descriptions I do have are minimal. I will update this as I figure it out.  I made this map in response to a new player starting off his Gamma World Career by discovering the Albuquerque Starport.  I'm pretty much "winging it" right now.

Update: 10 Aug 00

Feel free to use any of this for your own campaigns.  (The map is a little large, so you will have to use a photo editor to print).

These are the "main" towns.  There are many villages consisting of several family units scattered throughout the area, especially near the rivers.  Towns in BLUE are members of the "Greater Navajo Nation".

Aztec-
Population: 600
Tech Level: II
Inhabited by PSH (90%) and Mutated (10%) Navajo Indians.  Aztec also has some ruins which were ancient during the times of the ancients.  They were specially preserved by the ancients as a historical site and they still stand today. (Map). The Navajos have made this a sacred area.  To be invited to visit this site is considered to be a great honor.  DO NOT TRESPASS HERE! They have various excruciating tortures and other unpleasantries specially reserved for uninvited guests. The Navajos will warn people to stay away from the site unless invited. They will even explain the consequences.  Part of the "Greater Navajo Nation".  They will use artifacts.  See Gallup.
NOTE FOR REFEREE:  If the players still foolishly decide to trespass at the sacred site, the Navajos (every man, woman and child) will go on the war path.  They will not call-off the chase until every tresspasser is captured, or the last Navajo is dead.  This is a do-or-die situation.  (Basically the PCs just committed suicide.)

Albuquerque & Starport- See Mini-Module.
"New Albuquerque"
Population: 2000.  All character types.
Tech Level: II (moving up to III)
Albuquerque was rebuilt dozens of miles away from its old, poisoned location, but as the decades passed people forgot about the abandoned starport.  (See below)  These folk really don't care what you look like.  During the rebuilding process and the fight for survival, people accepted any one or thing, that could fight for the common good (against the Navajo) and who could help in the reconstruction process.  People here are very independent and do not have any particular alliance to any group, although there are members of various alliances here.  A truce has existed between New Albuquerque & the Greater Navajo Nation for 50 years.  They now conduct regular trade.
HISTORY: On a crisp, clear New Mexico morning in the spring of the year 2261, the great city of Albuquerque died. The sequence of events which caused the death of five million people began with the malfunction and failure of a reaction control force-field in the world's largest megafission reactor. A chain of coincidental failures, which according to all probabilities never should have happened, did. One by one the safety system's back-up fail-safe devices were engaged, and one by one they fused, short-circuited, and failed. In one searing moment the homes, businesses, theaters, parks, and inhabitants of Albuquerque, New Mexico, vanished in a wave of blinding light and furious energy. All that remained was a seething pit of flaming, molten earth 25 kilometers across.
Many miles away at the city's small starport, a few lucky travelers saw the thermal flash and watched as the city
rose into a boiling cloud of glowing radioactive dust. When Albuquerque's powerful broadcast power stations
disintegrated, the starport was plunged into darkness. The few remaining broadcast powered cars, bereft of
energy, ground to a halt. Swiftly the back-up power plant was engaged but, to the survivors' horror, the starport's ultra-radar revealed that the radioactive cloud was moving quickly toward them. With desperate speed they
evacuated the starport and shut down the emergency power plant, leaving the station's robots and other
devices in powerless immobility. Days later, survivors returned to the starport for the stores of preserved food
and water left there during their panicked evacuation. They found that the radioactivity remaining in the area
was too great, and the starport was abandoned permanently. Eventually Albuquerque was rebuilt dozens of
miles away from its old, poisoned location, but as the decades passed people forgot about the abandoned
starport. Now, more than 200 years later, the radioactivity is gone and only a barren desert remains. The
ever shifting sands cover the starport in a thick shroud many meters deep. Only the top of the starport's tall
radar tower remained above the surface of the burning desert in the year 2471.
(It was just recently discovered by a 1 meter tall, mutated ferret by the name of Ferrill Quickblade-an ornery, greedy and nasty little critter.)

Billings-
Population: 567. All character types.
Tech Level: II
The town guard charges a tax of 3 Domars per person for traveling on the road of the ancients, or the river.

Blue Water-
Population: 370
Tech Level: II
Blue Water got it's name due to a natural spring which is extremely fresh and cold. Inhabited by PSH (70%) and Mutated (30%) Navajo Indians.  Part of the "Greater Navajo Nation".  They will use artifacts.  See Gallup.

Deathlands- These are areas where nothing grows.  These areas glow at night, so it is relatively easy to avoid these areas.  There are several on the map:

El Paso deathland- See El Paso.
Roswell deathland- See Roswell.
Rover/Roy deathland- No one knows why this deathland is here.  No known records exist to give any explanation.  Many mutated animals come from out of this deathland and make attacks against Rover and Roy.
Santa Fe deathland- See Santa Fe.

Eden-
Population: 780
Tech Level: II
Inhabitants are 80% PSH, 15% Mutated Human, 5% Mutated Animal
This town is situated in a very fertile area with a fresh, clear river.  Various citrus groves, crops etc. To the east are the beginnings of the great plains, while several days to the north is the settlement and ancient city of Vegas.

This town's main attractions are a 1950's-style diner and an old "Howard Johnson's".  Both of these buildings are powered by solar generators which are completely maintenance-free.  (They will last another 20 years before failure). These establishments have been passed-down in the family since the apocalypse.

Rooms in the Howard Johnson's run from 5 domars a night, to 30 domars a night for the "Presidential or Elvis suites".  Naturally, the owner will set PCs up in the Presidential suite or the Elvis suite, unless they specifically ask for cheaper lodging.  All of the water/toilets/sinks still work.  Check-out time is 10:00 AM.

The diner 's exterior is of polished duralloy, complete with working neon sign!  The interior has booths lined against the wall, with a neon light running along the top of the wall. The windows are of "transparent aluminum".  Each booth has a small "box" with white buttons.  These buttons have letters (faded), but embossed on them.  Using these boxes, a person can make a selection of different 1950s-1960s songs to play.  Cost is one domar.  The waitress wears a hot-pink, synthetic (form-fitting) short dress.  This dress has large white buttons with white lapels.  A little cap completes the outfit.  She will always talk to customers like she is chewing on something.  When asked why she always "chews", she replies with, "I don't know, it is part of the job.  All of the waitresses have always had to do it."  Menus are original menus, printed on an indestructable type of nograin.  Pictures of menu items, descriptions (and prices) and numbers are still legible.

Local Law Enforcement:  The town has one permanent "sheriff" and four "officers".  Two officers work during during the day with the sheriff, and two take the night shift.  The sheriff and officers wear a type of "combat-armor" (similar to that in the "Fallout" RPG).  AC is 3.  Each is equipped with a Submachine Gun (SMG) (Slug Thrower B), with 2, 30-round magazines, short sword, club, and handcuffs.  The sheriff's office has enough armor/weapons to completely outfit 10 people.

During times of emergency, the sheriff can "deputise" as many people as is needed.  All he has to do is point at someone and say "You are now a deputy, follow me." (or something like that).  One officer usually is in the area of the diner and hotel, so as travellers enter town, they can see his presence.  He will usually great them, and let them know that "trouble is not appreciated in this town".  The only items not available are Coffee and Tea.  A synth unit in the kitchen can produce carbonated beverages (ie: colas).

Other than the above, the town is solid Tech II.

El Paso-
Population: Unknown
Tech Level: Unknown (VI)
While not in New Mexico, it is on the (current) border.  Since El Paso had a large military presence, it was hit with multiple nuclear, biological and chemical warheads.  (It had alot thrown at it.) The wind pattern spread the fallout, bugs & gas over an extremely large area.  The bugs & gas are long gone, but the radiation remains.  Adventuring into this city is fraught with peril!
Out in the radiated area towards the East, there is a mechfarm which has not been discovered yet.  The robots have removed the radiated topsoil and have a thriving farm.  Warehouses are stocked to overflowing with produce.  The robots are currently building more warehouses to store the produce.  This mechfarm is guarded by 6 security robots and 1 defense borg.

Fort Sumner-
(Adventure)
Was originally built during the "Indian Wars" of the late 1800's.  390 years later in 2260, the Government built a secret facility at the same location.  None of the original fort remained, but the Government decided to re-name the new facility after the original fort.  This facility was openly advertised as being a weather research facility to prevent it from becoming a military target.  To facilitate this cover story, actual weather experiments were in fact, conducted at this location.  Nobody remembers that this installation exists. (This is an adventure that I am working on...coming soon).

Gallup-
Population: 1500
Tech Level: II
Is the "Capitol of the "Greater Navajo Nation". Inhabited by PSH (95%) and mutated (5%) Navajo Indians.  After the Apocalypse, the Navajos "went on the war-path" (Remember, they are a tribe of Apache), and expanded a little bit.  They absorbed the Zuni tribe and the towns of Aztec, Blue Water and Kyeote.  All four towns are part of the "Greater Navajo Nation", which extends into Aridzone.  The Navajos are currently at peace and no longer have any plans for further expansion.  They believe in living in total harmony with the land and nature, but they will use artifacts.  This is their "Alliance".  No other Alliances are permitted to reside in their area.  They are very observant and keep an eye on their territory, using "smoke signals" to signal each other of intruders.  They especially hate the Knights of Genetic Purity (KGP). They are excellent craftsmen, specializing in a particular type of jewelry made of silver and turquoise. They are suspicious of strangers of any type, but are more than willing to trade.  They will normally allow passage through their lands if you are peaceful and no wanton destruction is done to any animals or the land.  This means no littering!  Navajo warriors paint their faces and bodies when going into battle.  They never allow KGPs to enter their lands.  It is usually not a good idea to have an encounter with a "war party".

Hillsville-
Population: 320
Tech Level: II
This is the only town around for many days of travel.  You need to be careful in this town, or you may wake up dead one morning, or working on the chain-gang building the road to Lacruz.

Kyeote- Pronounced (Kye-oat) GO there!
Population: 500
Tech Level: II
Inhabited by PSH (35%) and Mutated (65%) Navajo Indians.  Part of the "Greater Navajo Nation".  They are at Tech Level II, and will use artifacts.  See Gallup.  The reason for the large percentage of mutants, is that many inhabitants make scavenging runs into Santa Fe looking for artifacts.

Lacruz-
Population: 300
Tech Level: II
Due to the proximity of El Paso, This is a town of Radioactivists.  They make weekly pilgrimages to the deathlands surrounding El Paso.  Many pilgrims have entered El Paso to find artifacts, but few have survived.  (That is why the population is so low for such a large town).

Lordsburg- GO There!
Population: 728
Tech Level: II
There is a hill in the middle of town with a castle built on top!  After the Apocalypse, a group of SCA hobbyists banded together and re-established the feudal system in this town.  They used survivors to build the castle.  Each member (and spouse) became "nobles", while the masses became the peasants.  The members then conducted a tournament to determine who would be king.  Over the years, the title has once again become hereditary, and the King's "right of first" is in effect.  (This is where the king beds all brides on their wedding night).  This is considered (by the nobles) to be a great honor. If the King/Queen dies without a heir, another tournament is held to determine the new King.  The hereditary blood line also switches to the new King. They also speak funny;  I.E.: Hast thou a good time! Or,  "Dost thee wish for something to drink?" The feudal system is firmly entrenched in this town.  The nobles actually believe that they are of noble class, and the peasants believe that they are peasants.  The peasants are not treated harshly, nor taxed heavily.  Each peasant must serve for a number of days each year in the castle doing maintenance, cleaning, etc.  The peasants grow all of the food and supply the nobles and their families with all the food they can eat.  In return, they get the protection of the castle walls during times of war/strife.  Sunday is a day of rest, and everyone must attend church on that day or risk eternal damnation.  The priest is also a hereditary title. However if the priest dies without a direct heir, the assistant priest be elevated to the position, at which time the blood line switches to him.  Women are not allowed positions of power in the church.  The standing army consists of 50 soldiers, armed at Tech Level II.

Luz-
Population: 100
Tech Level: II
Luz is a backwater, "Kissing Cousin" town.  It is bordered by hills on the east, more hills to the west (several days travel) and deathlands to the south (also several days travel).  The nearest town is to the north, about 11 days of travel away. This place is in the middle of nowhere!  They are very in-bred, and many mutants reside here.  They are also very suspicious of strangers around here.   Prices for all services and goods are triple the normal cost.  This also due to it's isolated location.  Mostly, the people work in the fields growing their food, and sending-out hunting parties.  They distill a very strong corn mash here.  The locals drink it like water.  Non locals who drink this brew are at -2 to all actions for 2 hours for each glass of mash they drink.

Mechfarms- See El Paso and Mora.

Mora-
Population: 2000
Tech Level: III
Mora is lucky enough to have it's own mechfarm!  It trades the processed food packets for everything it requires, especially artifacts.  Each food packet has all of the nutritional requirements for one person for an entire day.  The Moran Defense Force has many artifacts with which to protect itself and the mechfarm.  The only other mechfarm is in the radiated area near El Paso. (not discovered)

Pinos-
Population: 183
Tech Level: II
No description yet.

Roswell-
Population: Unknown
Tech Level: Unknown (VI)
Reports were leaked that Roswell actually did have aliens residing in a secret underground base.  Paranoia caused this place to be hit with everything to include the kitchen sink!  The Radiation level is still hot (Int. 10).
Most of the town (not the people) survived intact due to odd fluctuations in the atmosphere (or could it have been the aliens?).  Many people who went to explore there never returned.

Rover-
Population: 650
Tech Level: II
Rover and Roy exist near a deathland and are under almost constant attack from mutated creatures which come from this area.  No one knows why or how this deathland came to exist.

Roy-
Population: 437
Tech Level: II
Roy and Rover exist near a deathland and are under almost constant attack from mutated creatures which come from this area.  No one knows why or how this deathland came to exist.

Santa Fe- GO There!
Population: Unknown
Tech Level: Unknown (VI)
Santa Fe was the capitol of New Mexico. This merited it taking a very dirty bomb (ground burst).  The large amount of radioactive dirt and debris scattered by the blast has maintained the radiation at higher levels than if it were an airburst.  The wind pattern spread the fallout over an area, but the mountains to the east prevented  it from spreading very far.  Adventuring into this city is fraught with peril!

Vegas-
Population: 7000
Tech Level III
Vegas escaped being hit with any nuclear devices, but it was still killed by chemical & biological weapons.  Some of the Ancient city remains in use, but the years have taken their toll on many of the structures.  Many structures bear the marks of renovation, but the citizens take pride in their city.  Artifacts are still occasionally found in the ruins.