It really really REALLY depends on where you're going.
Cali is pretty strict about the environment. Some beaches have certain spots where you can go to. Generally if people can go, dogs can too however some beaches will only allow dogs on a leash or no dogs allowed at all (generally crowded beaches.) Dillon's Beach (and whatever that camp ground next to it is) allow dogs and its a pretty, popular site. My favorite beach is up in Fort Bragg. That beach is on and off about dogs. Where people go, you can go but be sure to keep your dog on a leash when on trails. The trail is also for horses and many migratory animals breed there. The fine for an off leash dog is more than running a red light.
Down in So. Cal, I hear its much more chill. However most of their beaches are crowded so don't expect to be off leash.
And don't forget to have your animal wear a rabies tag. The more scenic the area, the more likely you may get stopped if someone doesn't see that tag hanging down.