Definitely need 4 wheel drive and decently high clearance. I only saw Jeeps, 4 runners, and trucks. Rocky and steep at parts, it was pretty damn rough. Then if you go the back way to the dunes there are spots of soft sand and going through the creeks. Good amount of pretty sites. We found a site on a Friday at about 7pm. Highly recommend Medano Lake for a hike in addition to the dunes.
Medano Pass is the route it's believed that Pike took into the San Luis Valley, and is one of the only primitive roads accessing the valley. The road starts in the Great Sand Dunes National Park, and runs over the mountain and exits on RT 69, or if you want an easy up and hard way down the mountain start off RT 69 and go to the dunes. From 69 to the top of the pass takes about an hour, and you only need high clearance 4 wheel drive for the last two miles of the 12 mile journey to the top. That's not the route we took.
We started at Point of No Return in the Great Sand Dunes National Park, don't worry there are plenty of places to turn back if you get nervous. There's DEEP sand throughout the first six miles, I aired down to 50 from 65, LOL. I figured I'd make it on 35's 12.5" wide, but I can definitely see where as the Sand ets softer I would have gone down to the recommended 20psi. If your going over the mountain have an air compressor to fill your tires when you get to the rocks. There's air at the ampitheater parking lot at the National Park, but no air on RT 69 until you get to a gas station at least twenty miles away.
We made it no issues, buy squeezing a super crew cab, F 250 through was TIGHT! It was FUN though, and my God the place is breathtaking!
Campsites start about five miles in and are spread all the way to the top of Medano Pass. This is National Preserve land, and it is primitive camping. There are fire pits and bear boxes, use the bear boxes as bear encounters are frequent. The sites are clearly marked, and nice size. DO NOT ATTEMPT TO TAKE A TRAILER, if you do you won't make it, I promise you that.
The Park, Preserve, and Forrest boundaries are clearly marked. To camp along the Great Sand Dunes National Park and the Preserve area of the road you must have a permit, free at the visitor center. I suggest reservations. After the Preserve it is a National Forrest and its first come first serve primitive camping only. You can stay for up to 14 days, as with most National land.
The 12 mile trip up from the Park takes about 4 hours, yes it's that rough. AND you will stop alot to take in the amazing views.
Even if you don't camp, take the drive, it's worth it. You will need high clearance 4 wheel drive, all wheel drive will not cut it here.