I believe the Art Museum area (Franklin Institute, Philadelphia Museum of Art, Academy of Natural Sciences, Please Touch Museum for Children) is about 2 miles from UPenn and Drexel.
If you are going to be in Philly for a couple days and have lots of time for sightseeing, you might want to look into getting the
CityPass...$54 for adults and $37 for kids...includes The Franklin Institute, Adventure Aquarium in Camden, Philadelphia Trolley Works, Philadelphia Zoo, National Constitution Center, and choice of The Academy of Natural Sciences or Eastern State Penitentiary. Unfortunately, the CityPass doesn't include the Philadelphia Museum of Art.