The quintessential California camping experience: check!
At Oceano Dunes SP, you can camp directly between the dunes and the ocean on the sprawling, beautiful Pismo Beach. This area is really recreational for ATV, 4-wheelers, etc... so on Saturdays and Sundays it's LOUD from ~10a to sunset. Fortunately, they're fun to enjoy and easy with rental places all over the beach.
Camping here is $10 and you get okay bathrooms at every post, but no fresh water. Since you camp with your car, it's quite easy to go in and out to grab extra supplies. You're allowed to cook and especially to build awesome bonfires here at night!
Be wary: decrease the pressure in your tires so you don't get stuck in the sand + bring WARM WARM WARM sleeping bags!