serious question about rush

I've read the previous posts about going around and getting interviews. Please don't laugh because I don't know. One PNM asked a question about how to get a bid to a top tier fraternity.
My question is: I'd like to look around, but what if I get a bid and I'm not ready to accept? Am I allowed to turn a bid down? If I like three fraternities and I get a bid from one, will they be offended if I decide to think about it?