Quick! Pre-theater place for tonight!
They've been mentioned on these boards before, so you might want to do a search for people's opinions, but Off the top of my head quick places might be Island Burgers and Shakes (also good salads) on 9th between 52nd and 51st. Also Hourglass Cafe 46th btw. 9th and 8th (closer to 9th). And Pietrasanta on 9th and 48th (I think)--for that place you'd need to call and make a reservation. Film Center Cafe, 9th between 44th and 45th (or a block north or south--I can't remember).
Also, there are plenty of places on 8th and 9th in the low 50's, high 40's that don't need reservations and can get you to the theater on time.
Hope that helps.