Here are the directions for all the BLM camping areas surrounding Quartzsite, both free and fee. Take your pick.
As for finding a spot, that won't be a problem. Each BLM area is huge, so just drive around until you find someplace you like. And, depending on when in February you'll be there, a lot of people will have already left the area since all the shows are in January, although a few of them do spill over into the first part of February.