I have a feeling most people are going to repeat what I say, but......
My school has 14 sororities and 24 fraternities. I've heard a lot of ugly rush stories, but in my 3 years here I haven't heard of a house excluding a girl based on race. I'm not saying it doesn't happen, but if you're a cool girl your chances are good that SOMEONE will want you as a sister, no matter what race you are.
Actually, being black might work in your favor, because many houses want to be diversified. They need some girls with good grades, some athletes, dancers, etc. You are right that the rush process is a lot of times mostly white, so imagine when you come to XYZ house and they're like wow! somebody different!
So actually you might have the upper hand over the rest of us
Just be your fabulous self and rush should go fine.