There is a KOA camground at 1186 San Andreas road (near the beach) in Watsonville. probably 20 minutes or so from Pinto lake.

http://www.koa.com/where/ca/05113.htm

Directions to Pinto From KOA
1. Start out going Southeast on SAN ANDREAS RD towards CREST DR by turning left. 0.8 mi.
2. Turn LEFT onto BUENA VISTA DR. 2.4 mi.
3. Take the CA-1 SOUTH ramp towards MONTEREY. 0.2 mi.
4. Merge onto CA-1 S. 0.5 mi.
5. Take the exit towards AIRPORT BLVD/FREEDOM. 0.2 mi.
6. Turn LEFT onto RANPORT RD. 0.1 mi.
7. Turn LEFT onto W AIRPORT BLVD. 2.1 mi.
8. Turn LEFT onto GREEN VALLEY RD. 0.5 mi.

Mitch