Lovely drive, you'll have a wonderful trip. In Albuquerque don't miss the Childen's Park. Sure it says children's but adults love it too. Across to Flagstaff, but I would go a bit farther and base in Williams, about 15 min west. Enjoy Circle of Pines KOA, stop at Bearazone drive through animal park, and the Grand Canyon is 60 miles straight drive north. Then cut up the 93 or 95 to Las Vegas, we enjoy the Oasis RV park, although Sam's Town (now a KOA) is pleasant. All of this driving is through mountains and deserts on good roads (as good as they get with the current non-existent level of road repair). None of the mountain climbs are stressful in a well cared for RV. Las Vegas to San Diego is desert with two long mountain grades, Baker grade (not to bad but it is a place where cars in poor condition overheat) and the Cajon Pass (west of Victorville, a very long steep grade often with strong cross winds) You can do it but you won't go fast. With all this said, if you have time, I would go from Denver down the 25 and then across to Durango/Mesa Verde, and down through Monument Valley spending a night at Goulding's. Then on to Flagstaff and Williams and Vegas.
Have a great trip.
