Many of the roads in Philly are quite narrow, just to be aware.
On days when nothing big is going on, the stadium complex ("Xfinity live") offers free parking, and there's a subway station right there. I've found that to be a convenient way to see things, but it's not the only option for sure. Their web site has the schedule and some details.
There's plenty to see and do in both Philly and DC to occupy one for quite some time, a few weeks at the least. The Philadelphia Art Institute is one of the finest art museums anywhere (and is enormous); I feel a little sorry for those who go there and only re-enact a scene from Rocky.