You can order pretty much any drink from any bar. They may not be able to make it at that bar, but you can order it. For example, we were in Skyline, the martini bar, and a guest ordered the drink of the day, it was something frozen. The bartender wasn't going to turn him away, but they don't have a blender, so he went to get it 'out back' but what he really did was go to the bar next door, which did have a blender, and brought it back.
Certain bars specialize in certain drinks: Skyline for martinis, Pink for champagne cocktails, O'Gills for beer, Cove Cafe for coffee and tea cocktails. According to the bartender we made friends with, most of the bartenders prefer you order drink of the day or frozen drinks from the deck, but you can order pretty much any drink from any bar and they will try to make it happen.