I just called the Wal Mart in Indio.... actually it's in La Quinta.... and the guy told me it's cool to park and sleep there. Talked to him for a min and he said a few rv's and cars park in the back of the lot and the store does not care. No security, which is good on one hand (won't be bothering you) and sketchy on the other.
I was wondering how many people have to resort to off site locations as I've never been to Coachella or Indio
If you don't know where you will be spending the night... maybe this is your solution? Approx 5 miles from the polo grounds. Hunker down in the car for a few hours of shut eye if you have no other place