The casual beach volleyballer can find pickup games at beaches the length of the coast; more serious players might want to concentrate on the Santa Monica State Beach nets or those at Manhattan Beach (which has about 200 nets). If you are truly obsessed, contact the California Beach Volleyball Association (800/350-2282) to see about amateur tournaments (grass-court play as well as sand); its California Cup State Championship tourney is held in late July and early August.
As for pro volleyball (www.avp.com), the beach volleyball played by two-person teams, check out the men's and women's tournaments held at city beaches in June, July, and August. The Association of Volleyball Professionals is the best place for information.