hmmm....how to discuss this and be P.C.?? ah, whatever...here ya go:
Philly is pretty diverse. in particular, in terms of minorities, there is a very large African American population. depending on where you go, African Americans are probably the majority or close to (i.e. west philly). Other than that, the other minorities are pretty well represented. I wouldn't come here anticipated the same kind of neighborhood diversity as in NYC (our chinatown, for example, is generally a source of disappointment to people expecting something similar to the one to NYC), but the city is certainly not, shall we say, "vanilla." one minority which i wouldn't associate with philly is latino/latina....i could definitely be wrong on that, but that's just been my impression over the last 21 years.
the other thing is that there are a LOT of people who commute into the city, so philly at any given time has people from the surrounding suburbs altering whatever it's actual demographics are, but i guess they would be there if you came to school here, so it really won't come into play too much unless you're looking at the patient population. the commuters are mostly caucasian, though i'm a contradiction to that statement.
ok, i'm done rambling...
hope that helps...any more specific questions, and maybe i could answer you better.