Keep an open mind. UNECOM resides in one of the whitest states in the nation but has a mission to serve the rural and underserved populations of Maine. To that end they have incorporated multicultural aspects to the curriculum to include the significant Somali refugee population in Lewiston-Auburn and Portland. That being said I think it would be important to talk to some of the URM students that have attended or are attending the school and get their take on the environment of the school (my guess would be that the perception would be of a welcoming environment based on my time there) and of the local area (as a non-URM I would have a tough time commenting. Pockets of the northeast are still quite racist [Boston's reputation is actually quite bad], but Southern Maine has always seemed pretty open minded). I do think there are ample opportunities to work with URMs as patients as well (Lewiston-Auburn, Portland, Biddeford [when I was there, there was a free clinic you could volunteer], and some rotation sites in Jersey and NYS). Talk to some students and alumni.
As for the other schools, a lot (most?) also have a mission serve the rural/underserved, but regionally they are going to have a different patient demographic. But, again, based on my experiences in Maine, finding out from some current/past students may yield some surprises.
Best of luck.