I think he may have meant USA not specifically United (UA), but I could be wrong.
There's probably a sticky in the spotter's forum but here's my synopsis:
Mojave - ask at the airport office for a $10 tour.
Kingman - fairly quiet here, you may get escorted access.
Victorville - no airside access, but they are used to people peering throught the chainlink
Goodyear (Phoenix) - no airside access, visible from public roads but local cops patrol regularly and will move you on with/without hassle (depends on his mood).
Tucson you know about.
Marana - absolutely no access at all, the single road in has a guardhouse way before you even get close.
Las Vegas - very few stored here now, but all visible from public roads.
Like the man said, you ain't gonna just 'wander round' anywhere.
hth