DP going up and down mountains

A little late to this party but since I had the same coach as the OP, I'll weigh in here. To the OP, you're overthinking this trip. Easy to do and worthwhile but, there are no grades you'll need to do any shifting up or down for. Your exhaust brake, assuming it's original is woefully inadequate. If you are keeping the coach, I would suggest you upgrade to the PRXB brake. You'll rarely have to downshift using that EB. Excellent upgrade for your coach. For your route, simply leave the keypad in D and go. Use the foot pedal to activate the exhaust brake when starting downhill and tap your brakes if you pick up too much speed. I've traveled all over the Rockies with my Dynasty and never once downshifted. Those are much steeper and longer than anything you'll encounter on your trip south. Enjoy the trip and be safe.

P.S. Ignore all the posts that rag on you cuz you're asking questions. Keep asking away...everyone learns that way....Dennis