I'm from NY, and did a archery hunt in Colorado last fall. I didn't hunt the areas your speaking of. But had very similar questions before I did the hunt as well. If your talking public land hunt, there's just so much area you won't have to worry alot about pressure during archery season. I went the last wk of bow. Which happened to be the wk after the muzzleloader season, and also the same wk as Cow rifle season. I saw a few other hunters, but nothing that had any effects on my hunting. The elk move around so much during the rut the pressure from other hunters is minimual.
To be totally honest you'll find thats the least of your concerns. Far as the ATV they're illegal on public lands, so I wouldn't be expecting to use one to get back in hunting or hauling one out. You'll be doing alot of footing. Horseback is the best way to go out there. Otherwise your limited to how far can hunt away from base camp setup, or like you wrote have to spike camp it.