braap, regarding going off campus, I think upper class (in year, not economic status
) students tend to go off campus (into Center City, etc.) more than freshmen, which makes sense. Also, there are enough students at Penn that you'll find a decent mix of students in terms of amount of time spent on or off campus. But hopefully some current students will chime in here and give their personal perspectives.
In terms of dorms, the condition really varies, and Penn is in an ongoing process of spending tens of millions of dollars to renovate the dorms. But the vast majority of freshmen do live with other freshmen. Again, hopefully current students will give you their perspectives.
In terms of food, that really depends--on what you're accustomed to, and on what you're comparing it to, etc. The food in the dining halls is probably par for the course as college dining halls go. However, Penn also offers lots of flexible and varied dining options, such as the food court in the wonderfully renovated basement of Houston Hall, and the legendary food trucks. Once again, we need some current students to chime in here with current impressions.