Im in oceanside which is in North County SD. I believe the closest RC airfield is in Fallbrook, though I have not made my way out there yet.
Well, technically, there's one in San Marcos, off of Twin Oaks Valley Rd. (belonging to the San Diego Wingmasters), but it's fixed wing electrics only - no multirotors or helicopters of any kind, which kind of turned me off of that club.
I belong to Palomar RC Flyers, which is the one in Fallbrook, off of the 15 and 76 freeway. They've got a large runway, everyone's really pretty nice, and it's a good club. Only problem I have with the field is getting out TO the field when it's rained recently (there's a small hill to go up to get to the field, and if it's rained, it's muddy).
And, on a side note, Teddy, if you want to check it out, this weekend, the 24th, would be a good weekend; they're opening the field to the public to come out, partly as a membership drive, but also to check out ASTREA, the San Diego Sheriff's helicopter division, that'll be landing at around 11:30 AM, with a barbecue afterwards.