Having been stationed in Yuma from '97 to '01 I can tell you it is pretty nice, (From the perspective of a Californian.)
Open Carry, and you can discharge a firearm outside city limits as long as you are 1/4 mile or more away from the nearest home.
4 prominent places to shoot.
#1 Adair Range, it is free, has a 1,000 yard range, as well as several other ranges. It is off 95, not too hard to get too.
#2 Not too far from Adair (actually on the way to Adair,) is an old, out-of-use 100 yard Army range that gets used for plinking all the time. Most folks park within 50 yards of the berm and either shoot stuff off the top or stand on the berm and shoot at all the crap behind the berm. Big foothills behind that.
#3 South of MCAS Yuma down 3E just before you go back on Marine land, is one of two rez dump spots. The Cocopah and Quechan dump their appliances and stuff back here, so plenty of targets. Game Wardens only hassled me once there, (Dove do occaisionally fly by,) but once they saw we were just plinking they bid us good day and rolled on.
#4 North of the base, north of Paradise Casino, (The Quechan's Casino) across the All-American Canal, is another Rez dump spot that some shoot at. I wouldn't go here, and I am not even totally sure it is in AZ. It is damn close to the border.
You can get more ammo at Sprague's at the intersection of 4th and 32nd, or Wally World.
One thing to consider, however. It is really close to September. Sept 1st at sunrise in Yuma sounds like Fallujah. Dove season is absolutely huge there. People come from all over, and the bluehair snowbirds are already starting to show up. The Game Warden is likely to be all over the place, checking for Cali peeps acting like idiots or poaching. Not impossible to have fun shooting during that time, but something to consider.
In fact, you could even make it a dove hunt/shoot. Most of the farmer's are pretty easy going about hunting their land, mostly only the Sunkist Orchards have no hunting signs posted.
The season is prety short, though, and if you HAVE to go to Yuma, the later in the year the better.
If the timing is right, I am down to go.
I will try to post a Google Sat pic of the ranges later.