Oh, Sorry WDW2. AllRighty then. Almost all car rental agencies allow one way rentals, at issue is cost. I don't know what agencies you have up north, but I would check out their prices online for 2 one ways and then give them a call. Alamo (when the website is working) or Enterprise are generally a little bit cheaper in Calif. & Nevada. You might be able to work out a deal since you will be bringing a car BACK to your local agency.
With that driving distance, another option might be a Park & Fly Hotel near SFO. I don't know which ones, but I know there are several that will let you book the night prior to your flight there, leave your car parked in their lot for the duration of your trip and will shuttle you back and forth to SFO. That might be a little cheaper than the 2 one ways. Good Luck.......Patti