I was at Penn for the interview weekend and have been admitted to the Bioengineering PhD program. I loved it there! The school is not exactly in the city but it's within walking distance. The hospital and medical school are right on campus so you could potentially do a lot of clinical work. The faculty and graduate students were super nice and friendly. A lot of the students live in Center City and said that the rent is manageable. Overall, it was a positive experience and Philly was just the perfect size for a city. I hope this helps!