I haven't been to California in some years, but in my trips out there, a few people looked visibly jarred out of whatever they were thinking about and then commented "You're not from around here, are you?"
Alternatively, once while walking in Manhattan a guy told me he could tell I wasn't from the city just by the way I was walking down the street. He then asked me where I was from and then told me a lot of locals are scared poopless of Southerners. He'd never been anywhere in the South, but I guess the stereotypes did him in. He agreed he would not mug me and try to take my wallet, and I agreed I would not do terrible, violent, swamp things to him, and we had a good laugh. I liked that guy, as brief as our meeting was.