"....but one option would be to take Hwy 11 from Indio" It's Hwy 111
A less direct route with more unique scenery and California history is to take I-15 down to Temecula. Then head south east on Hwy 79 through Warner Springs to S-2 (San Felipe Rd.) at Hwy 78 you need to jog west a short distance to catch S-2 again which is now called Great Southern Overland Satge Route. Some historic stage coach related buildings along the way, plus it skirts Anza Borrego Natl Park. S-2 changes names to Sweeney Rd and Imperial Hwy along the route. It ends at I-8 in Ocotillo just west of El Centro. Head east on I-8 into Tucson.