I live in the desert, 130 miles west of Tucson. There are many hard surfaced roads that have little or no traffic this time of year. Stick to main roads. Don't take a shortcut even though it looks like a nice drive on a paved road.

Double check your tires. They will take a beating. The heat on the highway can easily damage a poorly inflated tire. You don't want to be doing anything like changing a tire in the desert sun.

Lots of places without cell coverage, but if you are traveling the main roads (interstates or arterial roads) coverage will probably be OK.

Do no stop for hitch hikers. The rules of the game in the southwest are different. Not everybody is your friend. Especially near the border.

A lot depends on the specific areas you are traveling. Seek local guidance before you start your trip and if somebody says to drive 50 miles out of your way because of some "difficulty" there, drive the extra 50 miles.

In the unlikely event you have mechanical problems, stay with your vehicle. Get into the shade and stay there. If you are on a main road, somebody will come along to help. If you are alone with no vehicle, they might ignore you.

If you have not been in the southwest before, you will find it very interesting. Distances are long. Watch your fuel. Again, it really depends on where you will be traveling.

It sounds scary, but only if you have a problem. Like being in a blizzard or mountain storm, it is only scary because it is new to you. Mostly you will drive along in the cool comfort of your vehicle and enjoy the scenery.


Nomad.

Nomad nailed it.
Once off the main road you will often be the only car on the road for a very long time! Many times a road that looks well traveled ( & well graded) isn't. Also be careful of parking is dry washes, those clouds in the distance can create a gully washer where you are parked.

Are you afraid to mention security because of the group you are asking? You own guns. You understand guns. You are comfortable with guns. If you are uncomfortable flying with firearms, borrow one from your client when you get there.

ITS NO COUNTRY FOR OLD MEN

LOL my first thought when I read the title post was that it sounded like an amateur cleaner. No offense to the poster. This is a good place to ask for advice, and the others have done a good job, but i'd suggest a light sleeping bag. Don't rely on forecasts as the weather can change quickly. I live in the southwest. Guns of all types are readily available. If you are not comfortable with them you can always pick up a cheap can of pepper spray and ditch it before you fly out. If I can be of help simply let me know.

+1 on the sidearm. Should really consider a couple cans of fix-a-flat.

Be careful of counting on the cell phone for communication and GPS service. If out of 3G/4G range there are no maps on most phones. Bring a 'real' GPS and if possible pre-plan/preview your route on Google Maps or similar.

I've always been a believer in the utility of those giant orange plastic bags ... in the desert they can be slit open and used as flags ... or to provide shade.

Speaking of flags ... I might think it would help to have a very large bright "HELP NEEDED" banner. Does anyone make such a thing?

Not being a desert dweller I have to ask: Are insects a problem at night?

Reason for so much water....it isnt just for drinking,think heat stroke.Getting overheated can kill you.

With water pour it over your shirt,soak your bandana,soak your hat,it will act as an evaporation cooler and when you are HOT it may save your life.Heat stroke,if you ever had it you know its not to be trifled with.

Even if you have to wait 4-6 hours for AAA to come get you,those gallons of water can be a life saver just in that short amt of time.

Depending on the desert, I'd guess tarantulas and scorpions could be an issue [my inner arachnophobic shivers at the thought of a tarantula crawling over me in the night). Maybe some other creepy crawlies as well (research on the particular desert in question certainly seems prudent at this point). And seems like I'd heard horror stories of rattlesnakes in and/or under sleeping bags. I assume they are looking for shade during the day or looking for something warm in the night?

Guns. Well the poster did not say which state he/she will be traveling in.

AZ is OK as anyone can carry concealed.

Utah has strict gun laws, especially near urban areas.

New Mexico allows open carry but only honors permits from some other states.

TX has complex laws.

California has very restrictive laws.

Generally unless you are staying in AZ, I would be careful about carrying. If you intend to do so, check current laws for the states you intend to traverse. New Mexico just changed their permit law and I am not sure how it has been implemented.

Border Patrol: You may be stopped at a roadblock. They will ask you if you are a US citizen. Don't give them any grief. It is a rotten job. If you are "driving while brown". you may get asked some confusing questions. They are trying to see how nervous you are. You will also get the the funny questions if you are very white and driving a rental car. Folks from the north frequently drive to the border areas to get contraband. No tan means you are probably not local. They are looking for bad guys, you are not one of them.

Relax, you will get used to it. I live 30 miles from the Mexican border, in a very remote area. There is a war going on here. But somehow it dances around us and we seldom see it. We find backpacks with very good night vision glasses hidden under brush. There are used car batteries on mountain tops left over from clandestine radio networks.

All that and more. But you will probably not see any of this. The first time folks encounter the Border Patrol Checkpoints they sometimes consider it an intrusion. "What?? Stopping me?? I got my rights!!!" I hear it all the time. Consider the checkpoint a small window on reality. Be nice to the Border Patrol Folks.


Small crawley things...
Lots to learn about them. Mostly, don't sit on the ground. Don't lean against trees. Don't walk through underbrush. That is one of the reasons I suggest staying with the vehicle.

If you need to sit someplace, find a rock. Carefully check around it. Check it again. Look for small holes and cracks. If possible cover it with a tarp or something. Get your feet off the ground. Biting ants can cover your feet in seconds.

It is one thing to be in a wilderness you know. Quite another to be in a wilderness you do not know. I am from Maine. Being in the desert is realllllly enjoyable, but one has to learn the deserts ways. They are not the Maine ways.

Best advice I can give is to check your vehicle yourself. Especially the tires. Don't run low on fuel. There are many places where fuel stations are a hundred miles or more apart. Stay on main roads. You will cruise along in comfort (the roads are mostly very good) and wonder what all the fuss is about. Until you pull into a rest area and get out of the air conditioned car.

Enjoy your trip. The desert is HUGE with lots of exotic stuff to experience.

Nomad

I've tried it three or four times and it has never once worked for me. Apparently I'm a slow learner.