Welcome, from San Dimas! It’s hard to find free access to a lake or beach here in So. Cal. If you don’t mind camping in pay sites there are plenty to be had. Try IOVERLANDER app for spots. The sierras also have great places. If you want better beta PM me. The more info we have the better, how long of a drive? How much off road? How hard a trail. going by yourself? The family going, you and wife, you and buds?