I’ve driven it enough times. Foothill Blvd to the old 66 (which runs alongside I-15) will get you to Victorville and Barstow. It used to be you could follow much of old 66 to Kingman or Flagstaff and head toward SLC from there on highways 89, 160, 163, and 191. Going up from Flagstaff toward Mexican Hat you can make your way to Bluff (the inspiration for “Radiator Springs” in “Cars”, very beautiful) and ride up through there, its much more scenic (and less hot) than going up via Vegas. I spent my younger years on the Big Rez, and used to travel with the rodeo, I used to know all the roads in the region.