Mt. Diablo State Park
Getting there: Super easy, look for the tallest mountain in the area, drive towards it, boom you're there. It was expensive to enter the park... I think around $10 per vehicle, someone correct me if i'm wrong.
Campsites: The campsites are a decent size and fairly spaced out. All the campsites provide a old broken down picnic table, a bear box, a grill, and a fire pit. There are shared restrooms with plumbing to use.
The Park: Awesome. Big. Crowded. No dogs allowed.
What to do: Hike Diablo there are TONS of trails. Go rock climbing or bouldering in Rock City. Drive, hike to the top and check out the observation deck.
*will add my pics later.