UPENN '03 here. I'd say it is your best choice, 8% black population but there is a black dorm, all your typical diaspora student and performing art groups, all the major black frats and sororities and you're in West Philly/University City so there are black folk outside of campus.
Outside of my freshman year, I only really stayed in the black social circle. I came from a predom white boarding school (sim to Exeter,Andover,Choate, etc), so I was pretty much done with white folk at that point.
PM me if you have any questions.