Northern Quarter's a good shout, plenty of choice, small and easy to get around and close to transport links.

If you fancy pizza go to Dough, or Thomas St Restaurant's a nice place, not too expensive. If Asian cuisine then go to Ning on Oldham St. Then for drinks you can chill there, maybe share a bottle of wine sat outside the front if it's nice, or head down the road one way to Trof or Apotheca (personally I'd avoid Blu), round the corner to Common (might be a bit busy) or down the other way to Barcelona or Soup Kitchen.

And hell if the party really kicks off and turns into a late night you'll find Black Dog Ballroom's open late, and you can probably have a little bop.