Rincon Beach Park is near the Ventura/Santa Barbara County line just a few miles east of Carpinteria. Just take the Bates Avenue offramp (I always think of the movie Psycho when I pass that offramp. Every time.) off the 101 Freeway. Take Bates to the ocean and on the right you'll find plenty of free parking and easy beach access, with picnic tables and restrooms.
If you make a left turn off of Bates, there's a separate parking lot for Rincon Point, one of the most popular surf destinations in the world. There are a couple of restrooms on this side also, albeit not particularly pleasant to use :>
To learn more about Rincon Beach Park or to reserve the picnic table, visit www.countyofsb.org/parks/parks02.aspx?id=8078 or call 805.568.2465.
As of July 2011, there were no parking charges, which was a pleasant surprise.