This page might help also.
http://www.hikercentral.com/campgrounds/147036.html has listing of private places. Which some of which are not to spiffy looking. We had no problem in class C anywhere over there. Other than they are proud of their fuel prices.
At Pacific Beach SP... if you want a little drive to the beach or even driving on the beach, the best access road we've found to the beach is just north of the military Pacific Beach campground (where we usually stay). Fewer people.
Google maps shows it as...
Analyde Gap Rd
Pacific Beach, WA 98571
47.219089, -124.208088