I know that in my school there's NPC, AKA, and LTA. Most minority females here don't rush for NPC because they don't feel as if they relate to the majority white sororities. However, a few black girls rush each semester, and mostly end up with bids. I remember meeting a few other black girls during rush last year, and they mostly turned down their bids, saying they'll probably "do the Black Greek thing"

That was formal. This semester rush was informal, and the black girls that rushed did end up with bids and most ended up staying. The one girl that did drop did so because she just wanted to be a party girl...
I don't think that my school's NPC GLO's are rascist. There may be a few girls that may be clueless about other cultures... I believe that the reason why so many minorities don't rush is because they simply want to be around members of their own culture and don't feel as if they can be comfortable being the only one in their sorority.