Fire, how many ambulance services can you think of that hire seasonally? I've worked in OC at both a water park and an ambulance service. The ambulance services aren't going to hire anyone seasonally because they don't have a seasonal need, they have a long term need and plenty of applicants. As such, they aren't going to throw $6-700 (for Lynch Ambulance, when I left there, 18 hours of orientation, 36 hours (3 12 hour shifts) of field training at $10/hr with time and a half after 8 hours, double time after 12 for attendants. Add 3 more FTO shifts to get cleared to drive) for someone who can only work 2-3 months at best.
The theme parks and event medical services are the only options left, and unless the OP wants to drive an hour plus to LegoLand (Carlsbad), 6 Flags (Valencia), or depending where in OC the OP lives, Raging Waters (San Dimas), that pretty much leaves Knotts Berry Farm and the associated water park Soak City (again, to the best of my knowledge, Disneyland staffs their first aid with RNs).
This is, of course, ignoring the fact that the OP is a relatively new EMT (based off of age). In my opinion, new EMTs are not appropriate for the single coverage clinic style environment of first aid where a disposition besides "hospital" has to be made on every patient.