Nice, I live in San Diego, CA, ugh. They don't even like you on the school grounds or soccer fields. Signs everywhere in this state. I went to the Local HS which has 4 dirt Area, they call them baseball fields here, DROUGHT. I didn't see any signs so I will try it there.
Where in San Diego? I live in Vista, but know of quite a few places to fly. And you're right, there are a lot of signs around here, but it's mostly because a lot of people here are afraid of fire danger from Lipo batteries (and rightly so).
There are quite a few clubs around town:
North County
Palomar RC Flyers (which I happen to be a member of), which is based out of North County; we have a heli field and a 600' runway located right off of the 15 and 76 freeway. Our field, you do have to turn relatively quickly after takeoff, because there are to be NO flights over the 15 freeway, which runs perpendicular to the end of the runway; we've got orange flags out warning where the freeway area is so you don't over-fly it. Most of us are flying over what's known as "The Jungle", a copse of trees, poison oak, and tall brush that's home to road runners, tons of squirrels, rabbits, and other fauna.
San Diego
Silent Electric Flyers of San Diego (SEFSD) - they have a field located just east of the Sea World entrance, flying right near Fiesta Island. They've got a decent runway and have a drone course if you're into racing drones Parking on the weekend can get a little full because they're one of the largest clubs in San Diego, but again, lots of nice members and a definite camaraderie there.
East County
Weedwackers Aero Squadron - They fly just across from Cactus Park in Lakeside, right off of Wildcat Canyon Rd. They're full of great people, club members who are willing to help you fly and just have fun; the only problem I've found with their site is that they're butted up right next to a polo field, and the polo field owners hate any flyovers, as they're afraid you'll spook their horses, so you REALLY have to watch where you turn for a final approach to the runway.
South County
Chula Vista Model & Radio Control Club - as the name states, they fly out of Chula Vista. Again, a bunch of nice club people, but their field is about 600 feet from the International Border. Get too close with any planes, and all of a sudden you've got Border Patrol and Homeland Security wanting to talk to you. Most of the members will watch out for it and help guide you, but I personally don't like flying there because it makes me nervous that I'll accidentally over-fly the wall and my plane will literally get shot down (it probably wouldn't, but that's my worry!).
All of the above clubs require AMA membership to fly, as they are chartered by the AMA, and they do have club dues on top of that membership. However, most of the club dues go into things like maintaining the runway, paying for porta potties, club events (for example, Palomar RC Flyers has a 4th of July BBQ every year where it's free to the members; club dues pay for it, and there's a Christmas party where we have drawings for things like planes, a transmitter, free membership, etc.; they also purchase club planes to teach members and non-members how to fly RC planes!)
There ARE some other areas that I know of that you can fly at, such as Dave's Beach in Encinitas, but it's mostly slope soaring (which, if you're learning to fly, is NOT how you want to start!), or they're not too kosher to fly at due to fire hazards (i.e., if you go fly there, you'd better take a fire extinguisher and pray you can put it out if a lipo goes boom)