I'm an atheist in highschool. What should I do?

I live in Orange County CA which is very conservative and christian. I am a 16 year old gay leftist atheist. The gay part actually isn't what gets me into trouble. I don't know what to do. I've told people I'm an atheist and I get picked on for it and people treat me like a leper (very christian of them...). When Prop 8 was being debated I remember the people in my middle school chanting homophobic slurs and slapping 'yes on 8' stickers on everything, I guess it's because their parents. I was with a very popular girl in my school once and we were chatting, all of a sudden she asks me if I go to church. I answered "No". She asked me why and I said because I don't believe in god. She freaked out, called her friends over, and told everyone I don't believe in god. Her friends started asking me all these questions, and I could see she was crying a little. She asked what happened after we die if there is no God and I said 'nothing'. She apparently went home, told her parents and cried to them, and I was called to the principals office. The school principal told me not to speak out your personal beliefs, I understood and said yes. But now I still get harassed. I can tell that everyone knows I'm an atheist and hates me exactly for that reason. I was popular until I answered that one question the girl asked. I can tell even the teachers treat me differently. I go to a public school btw. I hate this. I hate everyone in this piece of crap southern california beach town. I can't talk to my parents about it, since they are ultra conservative bible thumpers. I've had to HIDE the books "The God Delusion" and "God is not great" under my bed so they can't find out. I will never tell them who I really am until I move out... I don't want to be kicked out of my house when I'm 16.