if you can find a hotel in Indio, they are (were) pretty cheap. we've never paid more than $120 a night (and that was for the nice room on the golf course).
getting in and out of chella can be an utter bitch. its taken us anywhere from 30 minutes to 3 hours to get to our Indio hotel before after the show.
if you plan on staying til the end each night, i would try to find anything within walking distance...its priceless, trust me!
but most of those places are booked by now i would think.
i reserve my room in October each year, then cancel if i dont need it