I don't key out manzanitas when hiking with my kids...the two just don't go together (yet!), but my off-the-cuff ID would be Arctostaphylos crustacea.
Possibly A. crustacea.
The walk-in campsites at Butano State Park are situated in a stand of second-growth redwood. The understory is a bit beaten down around the campsites, no surprise, but otherwise in pretty good shape just beyond.