Try Indian Waters in Indio. Don't know any details about it, but they totally renovated it a couple years ago, and it looks nice.
Another place is Carefree RV Resort in La Quinta.
If you're a member of the Elk's Lodge, they have about 50 spaces (30A, water, & on-site dump) off Madison St. in Indio.
I've found that this site
RV Park Reviews ususlly gives you a pretty good idea about what's around where you're planning to visit.