Go to HireMarines.com. They have many jobs every day posted by residents and companies in North County that want to hire you on weekends and when off duty.

Here is an example:
Serve Dippin' Dots ice cream, run cash registers, help maintain clean, organized sales stand, inventory control.

Beach Soccer Championships at Oceanside, CA Harbor
Sat 5-14, 0800-1630
Sun 5-15, 0730-1800 (Can be 2shifts)

Venue is across I-5 from Main Gate Camp Pendleton on the beach
Work by the beach, part inside small food service trailer, part outside
Includes 1 meal
Parking limited, come early, be dropped off or walk in
$13 hr.