Residents only beaches are illegal in California since the entire coastline is public land.
I visit California every couple years and it's one of my favorite vacation spots. My favorite beaches are the small ones with tiny walkways between residential homes. You feel like you're trespassing, but you're not.
I've also made use of dozens of parks in CA as my son was a professional BMX rider for a time and we went on a tour of as many CA skate parks as he could ride. It was a good time and we were allowed access to every park we visited.
https://www.sfchronicle.com/travel/article/Santa-Cruz-s-priv...