NBN, look at the info I listed in one of my first posts. We do have some degree of cooth here.
Mexican...hmmm...that could be the case, but Chicago has a ton of Mexican restaurants too...and only about half the people in the city are really fat.
I would not recommend making your base camp Broad and South if you can avoid it...the area there is a tad shady. I would only use that area if you're using the Subway (aka the Broad Street Line/Orange Line). Most of the restaurant, bars, and shops on South Street are between 2nd and 11th. You'll also find side street shops and restaurants off South Street between 2nd and 11th.
Will you be driving while in Philadelphia, NBN? If you are, your best bet for parking is on Lombard St between 2nd and 3rd (Lombard is one block N of South St.). It's a good starting point too, as most of the cool stuff on South is between 2nd and 6th.
Let me know when the time gets closer NBN...I'll be glad to join you for a pint or two.