Before, I begin, let me suggest you try this in the general PA forum, as Williamsport is not really in NE PA.
Anyway, I grew up in Montoursville, where our exposure to minorities was a foreign exchange student from Latin or South America! So to me, Williamsport has a high percentage of minorities. I did go to Kindergarten at the old Transieu (sp?) school in Williamsport near the old Bethune Douglas community center and I think there were maybe three or four black kids in my class. But keep in mind also that this was 1968, when the times, they were a-changing.
I think if you're looking for racial diversity you will find it in Williamsport, and I don't think people will stereotype you as being addicts or thieves unless you move into the areas where those types of people (of all races) congregate.
Good luck if you do make the move, and again, try asking your questions in the regular, main PA forum.