I have some friends who manage to drive around Columbia SC with Darwin Fish and pro-science stickers (not explicitly atheist), but I live outside the capital and I don't put anything on my car. I can't afford repairs and in SC the farther from a city you are the worse it gets. I'd be concerned for my personal safety in some small towns in SC if I advertised that I'm an atheist.
I'm not anti-Christian. I'm anti-stupid.