november is big in California, so 3-4 foot is everywhere, pretty consistantly. Its when the swells start shifting from the S to the W or NW. where in California are you going.
Yes there is localism, especially at the mellower longboard spots; that is if you go out there without scoping the break first and act like you are Joel Tudor but really aren't. You'll be able to spot the locals immediately. they will know exactly where and how the break works and have it dialed in. Do not get in their way, wait your turn, be polite and most importantly check you are not dropping in on anyone. There are plenty of waves, when its your turn/wave, go and rip. Above all be polite. Its packed enough here.
sharks?! I have surfed breaks where they "supposedly" are lurking. Sharks are attracted to seals and/or dead things on or near the beach. so unless you are surfing in a seal spawning area (which is highly doubtful as seals are more localized than Huntington Pier on july 4th) or there is a dead thing at the water line that the shark can smell, you have very little to worry about.
Caveat: the above is not insurance, its assurance. weird things can happen, karma etc, or you just happen to be surfing in Santa Cruz where localism and sharks are abundant.