We always eat at the bar in Signature restaurants. Those offering a full menu are:
California Grill
Citricos
Flying Fish
Narcoossees
Jiko
Shulas
Blue Zoo
Il Mulino
Fultons
Artist Point and Yachtsman have no restaurant bar, but have adjoining bar/lounges. Stories vary as to whether or not you can get a full meal.
We've had great success w/o reservations, but only by going early. The only time we've been unable to get a bar seat is at Blue Zoo and Shulas when the Swan/Dolphin have large conventions. Those times the bar is SRO almost as soon as they open.
Hope this helps!!