All the beaches in LA County require dogs on leash, although I drive the coast to work and see dogs on the beach every morning with no leash, LOL!
One of my favorite beaches in LA County used to be Leo Carillo State Beach (Luna spent many days there slobbering on surfers, LOL), but it is now restricted to on leash only, so I haven't been there since. Other beautiful beaches are the "pirate coves" of El Matador, El Pescador, and La Piedra...if you go early, I doubt there would be a problem taking a dog there. These are located just north of the Malibu Colony. They are 3 small coves next to each other that are just stunning and when the tide is out, you can go through natural rock tunnel formations to go from one to the next. Lots of photo shoots happen there because of the natural beauty.
One of my favorite beaches is in Santa Barbara (about 1-1/2 hrs north of LA) - Hendry's Beach (also called Arroyo Burro). It's huge, and even huger when the tide is out. If you go to the right onto the beach at the entrance, it's on leash, if you go to the left, it's off leash....so everyone can enjoy the beach. I prefer the beach when the tide is out, and as early in the morning as I can get there, when there are few dogs.
The Huntington Beach Dog Beach is "famous"
- so too crowded for my liking.