Don't be afraid to stand up about it. In my experience, most people (not all, most) who use the Bible to back up their homophobia are *blissfully* unaware about the actual context of Leviticus. The look of shock when you bust out the actual context of the book is usually priceless. :P

I don't know enough about your parents to comment on that, but at the end of the day, they're your parents. They should love and support you regardless. Granted, I have heard some very different tales from people coming out, which is incredibly sad IMO, but they should be in your corner regardless. How do you think they'd take it if you were to tell them?