No, the California Vehicle Code explicitly defines a vehicle as excluding human-powered devices and therefore excludes bicycles. But the cyclist himself is assigned all the 'rights and responsibilities' of a vehicle operator. As stated previously, the legality of cyclists on sidewalks is left unaddressed by the CVC and is therefore up to each local authority to govern in their own jurisdiction.

I also note that the local law quoted by oddjob for Sunnyvale appears to only prohibit sidewalk riding in places where there is explicit signage in place designating that particular sidewalk as being for pedestrian use only.

Although I don't advocate cycling on sidewalks since I consider it to generally be more dangerous than riding on the roadway, it is legal in quite a few locations in California and the local laws have to be checked to determine where.

CVC 670:
A "vehicle" is a device by which any person or property may bepropelled, moved, or drawn upon a highway, excepting a device movedexclusively by human power or used exclusively upon stationary railsor tracks.