We went most of the way but turned around before reaching Presidio. As I recall there is one low pass to get thru. You'll be driving thru the Big Bend Ranch SP, keep an eye out for the movie set village. Dead Man Walking and a number of other shows were filmed there. I don't think I'd drive a Class A down into that set tho. But you can park on the road and walk down.
ContrabandoOtherwise the road is a mostly flat two lane highway in good condition. You are following the Rio Grande for most of that trip. There are several access points. I don't recall any services along the section we drove on.
You'll notice the non-existent security along the river. You could walk right across since the 'river' is no more than a foot deep and there are sections where it is bone dry.
Oh yes I almost forgot, there is a slot canyon that follows the course of the Rio Grande, or would if there was any water in it. Closed Canyon:
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