IMO, UCLA could be the #2 or #3 if they put together some good seasons. But as things currently stand, I would not put them above USC, Oregon, Washington.
As for Northern California (outside the Bay Area) and Central Valley, I agree that it is definitely not Stanford or Cal territory.
In the vacuum of loyalty left by the non-appeal of Stanford and Cal (pretty much Bay area only), and no major college team in the Sacramento metro area, the FBS team that seems to fill the void the most is Oregon. Fresno State definitely has fans (particularly in Fresno). But Oregon flags, bumper stickers, etc. are the most common.