I've seen guides in Co. use horses but a quad will be restricted to the roads just like my truck is.
The Forest Service will be all too happy to fine you for going off-road, I've seen it a number of times...just wanted you to know!
"Camping places fix themselves in your mind as if you had spent long periods of your life in them. You will remember a curve of your wagon track in the grass of the plain like the features of a friend." Isak Dinesen