As a franchise attorney, I recommend you visit the California Dept. of Motor Vehicles website at www.dmv.ca.gov as this will provide forms and answers to your question.
Generally speaking, ff you are a visitor in California and have a valid driver license from your home state, you can drive in California without getting a California driver license as long as your home state license remains valid.
But if you become a California resident, you must get a California driver license within 10 days. This entails paying the standard fee, taking the vision and driver's exam, etc. Residency is established a number of ways, like voting in a California election, paying resident tuition, filing for a homeowner’s property tax exemption, or "any other privilege or benefit not ordinarily extended to nonresidents."
Kevin B. Murphy, B.S., M.B.A., J.D.
Attorney at Law
Director of Operations - Mr. Franchise
FRANCHISE FOUNDATIONS APC
If you have a valid Washington state license, but are now a resident of California, you should be able to obtain a Cali license. Just go to the DMV and submit an application.