I did a 10 speed bike trip down the coastal highway of California one time.
You can't always trust your memory in cases like this, but I'll offer you this impression I had anyway, because it seems to apply here.
I was peddling south between San Diego and the Mexican border. I came to this intersection where I could head east towards San Clemente (I think it was), then make a connection north. I headed east, and in what seemed like no time, hit this small town. I don't remember it's name.
Before I hit this town there was greenery. There was a small park in it. As I headed out of this town on the eastern side it was like a gateway into the desert.
I know this to be a fact, because I hit a sandstorm and slept under a scrubby bush. When I awoke, I looked back the road and I could see the exiting such and such a town sign.
Now I don't know if Sunnydale is just a Springfield-style elastic city or not, but given my impression of the topgraphical possibilities of Southern California, I'd say having a town in that region, with desert on one side, and the ocean in reachable distance on the other is a possibility.