If your RV or motorhome is 40 feet long or less, or your RV plus a trailer is 65 feet long or less, you can travel virtually anywhere in California. For single-unit motorhomes (and tour buses) that are over 40 feet up to 45 feet in length, contact Caltrans staff in the Office of Truck Services, Truck Size Branch:

Casey Robb
Manuel Fonseca
Phone: (916) 654-5741
E-mail: hlegaltr@dot.ca.gov

You will find information about 45-foot motorhomes and buses in California at this url: http://www.dot.ca.go/hq/traffops/trucks/ (Scroll to topic #6).