If you are coaster fans, then California's Great America is a great choice. If you visit Knott's Berry Farm or Knott's Soak City Chula Vista, look into getting a Platinum Season Pass, or upgrading a lower version you already have, as they are all Cedar Fair run parks.
Also in the Northern California Bay area, there is Six Flags Discovery Kingdom, a former MarineWorld park that has turned into a 3 part park, one Part Marine Park, one Part Zoo, and one part Rides and Coasters. And if you have a Six Flags Magic Mountain Season Pass, you get into SFDK for free.
Also in the area,, Santa Cruz Beach Boardwalk, which only has a couple of Roller Coasters, but still a fun day right on the beach. Slightly similar to Belmont ark in Mission Beach, but much larger. (Both have a "Giant Dipper" and the family that runs SCBB has the operating contract for Belmont Park.
The other one is Gilroy Gardens in Gilroy. a small park with rides for kids, and a couple of coasters. Managed bu Cedar Fair, so a Cedar Fair Platinum Pass gets you in for free.