I've driven right up on deer with 4 wheelers, but never really took them for hunting. For both mule deer and whitetails, vehicles don't seem to affect them if they're parked awhile before your hunt, or parked far enough away from to begin with. I do a little whitetail hunting and we'll park in the same place, which will be around 200-400 yards from the stands in the area. That's a really quick walk, and if you shoot a deer, go ahead and grab your atv.
Basically, if you're concerned, just park a ways away and walk 10 extra minutes.