We have been away for awhile - sorry! Florence has been (from what the Florentines have been telling me) unseasonably cold, and finally wet (which is normal for this time of year) - very wet. The rain sometimes hasn't stopped for days.
Here are some quick food notes:
For focaccia and pizza, if you see a Pugi shop, give it a try. Very tasty and fresh with a big selection. There is one on the south side of Piazza San Marco, and also Viale De Amicis 49r and Via San Gallo 62r.
For a really cheap self serve in the center there is a cafeteria just two blocks west of the Baptistry called Leonardo. It is upstairs above a clothes shop. Via Pecori 5. Fast, inexpensive, and pretty good (especially for the price - lunch for a family of four - 15 €).
For something finer, if you are around Piazza Santa Croce, try Boccadama. Whether it is a pannini at the bar, or a sit down lunch or dinner, this is a high quality place with terrific food and an extensive wine list. On the south side of the piazza at 25-26r. On the web www.boccadama.it