There are not very many secondary roads across the desert but one option would be to take Hwy 11 from Indio South along the North shore of Salton Sea and then hook up with Highway 8 East to Casa Grande, then I-10 to Tucson. West of Tucson there is a neat State Park a Picacho Peak that we like to stop at. East of Tucson at Benson take Hwy 90 South abou t 15 miles to Karchner Caverns SP. There is a nice RV campground in the Park. The cave tours are awesome, especially the Throne Room Tour that takes you to a giant formation called Kubla Khan.