Wawa Welcome America is happening now through July 4th, so there are all kinds of free things going on in Center City (sounds like you're in University City? I don't know Philly as well as I know other places!) and in the historic district - complete schedule and whether or not you need to reserve tickets here: https://welcomeamerica.com.
DH likes cheesesteaks from Tony Luke's; I think they're OK, so I get the roast pork there.
I second the roast pork at DiNic's at Reading Terminal Market, and also recommend whoopie pies (especially like the "peanut butter cup" and Guinness-creme ones, but you can't go wrong with a classic!) or a slice of cake (you only need one slice and you should share it with someone else; this month's flavor is the Sundae Cake, but I recommend the Elvis cake if they have it!) from Flying Monkey Bakery and Beiler's Doughnuts (DH and I recommend the blueberry fritters and the Elvis doughnut) ... oh, and Basset's Ice Cream.
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Liz
DD (3/2010)
"Make mistakes! Get messy!" - Miss Frizzle