Lunch options near PA convention center??
Reading Terminal Market is right across the street. http://www.readingterminalmarket.org/
Try DiNics for roast pork sandwiches (lines can be long), Becks for pretty credible cajun, Hershels for great deli, Thai stand is very good, 4th Street cookies or Bassetts Ice Cream for dessert, lots of other choices - avoid the cheesesteaks - there are far better places elsewhere.
Gotta do the Reading Terminal market right across the street as previously mentioned. All of the previous places are the vendors to hit. I'd also avoid the diner. If you can swing DiNic's their roast pork is amazing.
Do note that Barbuzzo is only open for lunch on Friday. Also next door (and open for lunch all days) is Zavino for excellent pizza. Afterwards head to Capogiro for gelato across the street. It's all a few blocks and a street over to the south on 13th St.
Of course, first choice would be Reading Terminal Market - exciting, with lots of options. It does get very crowded, but it's a must-see.
A quiet place with good food is Vietnam Palace, on north 11th Street between Race and Vine.
There are good places on 13th Street north of Market - you can browse this Board for info on Barbuzzo and others.
Upscale - on Broad St. there is Capital Grille, McCormick & Schmick, etc.