Several state parks in California have hike-in, and bike-in site at designated camping areas. Unlike dispersed camping, this often means developed campgrounds with fire rings, a picnic table, toilets and sometimes even running water and showers. Most developed drive-in campgrounds in California charge from $20 to $35 per night, but the walk / bike sites range from free to $7 per night.
A spot check of campgrounds with Reserve America shows the bike-hike campgrounds are not available for reservation; it appears they’re first come first serve. I’ve heard of a few times when people arrive at an occupied bike camping site, but the two groups share the site and make new friends. Note the bike camping sites are small compared to the drive in sites!
Not listed below: The backpacker camping sites along the lower six miles of the Skyline to the Sea trail in Big Basin State Park are bike accessible from Waddell Beach on Highway 1. These camping sites are popular with backpackers and advance reservation is required. You’ll share this trail with backpackers, equestrians, and numerous dayhikers, especially on the weekends.
Note: On the California State Parks website, you’ll see “walk-in” camping sites listed. This means you park your car in a parking lot and then walk back into the woods or to the beach a ways to your site. You’re still free to bike there, of course.
The information below comes from California State Parks, but may contain typos or be outdated due to state funding issues. I know of one camping area that closed the bike camping, for example, to cut costs. Before you embark on your trip, contact the state park or state beach to verify this information.
List of California State Parks with hike-in / bike-in camping
Del Norte County
El Dorado County
D.L. Blisss State Park 2 night maximum
Los Angeles County
Donner Memorial State Park 2 night maximum
San Luis Obispo County
Santa Barbara County
Santa Clara County
Santa Cruz County