I've stayed numerous nights in Palm Springs (PSP) in my unpainted and unlocked RV... tied down outside on the ramp at Signature, no issues. They're located on the west side just north of the airline terminal. I think they have hangar space available, but it's pricey... their tiedowns are fine. Last time there I called across the field to Atlantic and they had ramp parking only, no hangar and no tiedowns. You might try 'em again to see if that's been changed.
Speaking of pricey, it is Palm Springs, so everything is expensive. Signature has a tiedown and ramp (handling?) fee, but the ramp fee is waived if you buy 7-8 gallons of their overpriced gas. You might consider taking on a minimum fuel load there and head to Thermal, Big Bear or Flabob for much cheaper gas. And bring your own oil... the greedy slimeballs at Signature actually wanted to charge me 14 bucks for 1 qt of Aeroshell 100. Yep, fourteen dollars for one quart of oil. Insane.
Someday I might consider parking down the road at Bermuda Dunes or Thermal, but my brother's place is so close to PSP, so convenient... but you gotsa pay for convenience I guess.
Good luck!
