This is probably coming a bit too late, but anyways...
If you want to live in "the city", you're talking about Center City, which has the borders of the Delware River to the east, the Schuylkill River to the West, Race Street to the North and South Street to the south. Just about anywhere within that border will put you "in the mix", where you can walk any and everywhere interesting.
Rittenhouse is the ritzy, high-priced area of Center City.
Old City is on the eastern edge of Center City on the banks of the Delaware, and has a lot of 20-30 year-olds wanting a more laid-back lifestyle. Good restaurants and bars in that neighborhood
Society Hill, where I live, is the old, established neighborhood with lots of 200-year-old homes (and newer ones interspersed there, like mine). Lots of the homes are divided up into separate "apartments" that you can rent. I'm convinced it's one of the most picturesque neighborhoods you'll ever visit in the US; after all, Independence Hall National Park and the Liberty Bell are in the neighborhood. But homes here can come at a hefty price...
Queen Village, while technically South Philly, has some quaint charms of Society Hill but at lesser price. It's historic in its own right, but it stands out due to lots of the very cool "BYOB's" interspersed in the neighborhood. A very quiet neighborhood as well, even if it's near the raucous South Street.
The Fairmount/Art Museum (the same art museum in the Rocky movies) area is also technically outside of Center City, but still brings a lot of downtown charms to the neighborhood at a fraction of the downtown price.
"Ya gotta love livin', baby, 'cause dyin's a PAIN IN THE ASS!" -Frank Sinatra
[This message has been edited by True Anomaly (edited 9/21/2009 8:51p).]
