Good to hear that you all are interested in Pitt Med.
Acceptances are usually sent out at the end of February. The student interviewer who interviewed you will get the result if you got in, so some may send you an email with the good news even before the official letter arrives.
I'm not sure if the applicants who get interview offers before their applications are complete get in on a higher rate, but that makes sense since they are usually "stronger" applicants.
As for the class make-up, about a third of our first year class is classified as "Pennsylvania residents." The next biggest group is from California with about 15 or so students.
Concerning the yield rate, our class was an anormaly, needing about twice the number of acceptance offers to close out the class. I'm not sure why that was the case, but maybe it had to do with the location. Pittsburgh is usually not consider one of the "hot" spots for young professions, even though it is nice because it's more of a cosmopolitan city with a small-town-feel to it. Regardless, if you pick a medical school, you should pick one that feels right to you and that has the opportunities you want, especially if it is medically-related. You can always move to your dream location for residency.
Hope that helps clear up any questions or concerns.