All 3 states offer ample opportunity for Mule deer. I've never hunted Montana or Colorado but Wyoming and both of the others would have a lot of options that you could hunt public land from a hotel or camper if he doesn't want to hunt out of a tent.
He might reconsider if he saw some of those wall tents that outfitters set up. They do drop camps where they pack you and your gear in and then back out at the end of your hunt. They have the tent set up and cooking utensils and wood stoves for cooking. That's what I'm planning to do this year for my first backcountry hunt for elk. The drop camps seem to be a little cheaper in Montana than Colorado from what I've researched.
It's possible to hunt from a motel if he must have a warm bed but it will take more walking in and out at the start/end of each day.
Plus you could probably get a bigger trophy and better overall experience if you get in deep (away from the crowds). Good luck I hope this helps a little.