I'd recommend going down US 191 through Moab Utah. Absolutely gorgeous plus right next to Arches NP and close to Bryce Canyon NP, Natural Bridges NP. The ride out there from San Francisco would be really nice too. You'd take I80 east through Lake Tahoe then Reno Nevada then Salt Lake City Utah. Go south on I15 from Salt Lake until you get to Provo then go east on US6 until you get to I70. Go east for about 15 miles then turn south on US191. That will take you to Moab. When you leave Moab you can backtrack to I70 and go west until you run into I15 and turn south. This will take you to Las Vegas and onto Barstow in the Mojave Desert near Death Valley where you can either continue onto Los Angeles or turn north towards Bakersfield US58. If you continue on to LA you can catch the Pacific Coast Hwy US1 which will take you back to San Francisco and is the most scenic highway on the west coast. Just a suggestion from one who has traveled these routes lots of times.
Moab Canyon
