When you step out of the hotel in Piazza Ognissanti turn right and take the street that goes toward the city center, in the opposite direction from the Grand Hotel, can't remember the name off my head. On the other side of the street from the Excelsior there's a nice shiny neighborhood bar that has good croissants and costs a third of what you pay in the posher places near Piazza della Signoria and Piazza della Repubblica.
Unfortunately it's not open during the weekend (it's a nice wine bar at night too)