Glamis, Gordons Well, and theres a couple others which are part of the Imperial Sand Dunes. You can buy an out of state green sticker that lets you run all of them, its like $20 if I remember right. Me and my friends are out there a lot and weve never gotten bugged to get one. If you have a flag, helmet, a copy of your title or reg to prove you didnt steal your ride, and arent too intoxicated they leave ya alone. Glamis has cop issues, Comp (Olds) hill gets closed at night, and Ive heard stories of them kicking people out with pepper spray bombs (no s**t, they hit my friend on his golfcart with one) and other BS. My favorite actual riding place is Gordons Well which is more south towards Yuma AZ.