You can't drive a vehicle inside the polo field. Onsite camping is just rows of tents and RV's. The adjacent field lots will be filled with parked cars. The streets surrounding those are indio city streets so whatever the rules are for driving atv's on city streets would apply.
I have the same question about ATV's I'm not planning on riding them at the show, I just want to know if we can even bring them in. I'm going to have mine as part of a continued road trip up to Pismo after stagecoach. Let me know please if you have found out anything more!!