I went to a big public school and I would say the greek system is fairly diverse.
I would say that a fairly good amount of the houses have minorities. And not just one either. As a african american in a historically white sorority, I picked mine because when our IHQ was recruiting they were looking at girls of all races, years in school, personality, etc. And thats what they continue to look at. Like someone said it all depends on the area and just how comfortable people are. I am sure some people think about a person's race when they rush after all being Greek doesnt eliminate issues society deals with, and as another person said I might not get the welcome I would like from other chapters in my org. (after everything my org has been through dealing with race I should hope I would get a nice one). If anything plays an issue on my campus in rushing its more likely to be what year in school you are and sometimes unfortunately how much money mommy and daddy have