The way I see it, is that every parent assumes, or subconsciously believes that their child is straight. They may not even think about it. They don't ASSUME you're attracted to the same gender, because society's view of a perfect family is a husband and a wife an their little munchkins. That's what your parents usually assume you will be a part of when you grow up. But my view is that NO ONE has to come out as straight to their parents. They don't sit them down and say "Mom, dad, I'm straight." So I don't think you should HAVE TO come out to your parents as being attracted to the same gender. My advice is come out to them if you're confident enough, and if you're not, then just be with whoever you care for and let them find out on their own. Coming out is not an absolute, no question you-have-to-do-this kind of thing. Just be yourself. :)
Look, if they love you, like real parents should then you'd have the faith in them to tell them
;P fingers crossed - if they get angus, well, I dunno, I'm not good at spewing secrets I usually just possum. so I've got not much experience to tell. But seriously, just remember to keep cool and take the first shot (when they start shouting) Try and expect the worst and try and work out how you'd end it in an understanding manner.