Location, Location, Location! 3 minutes from Santa Croce, then another 3 minutes to Piazza Della Signoria, Uffizzi gallery, Palazzo Vecchio and another 6 minutes to Ponte Vecchio. You can do it all on one day!
There is a very convenient Bus # 14 from SMN Florence station to her house. From the stop it is a 5 minute walk. We caught the bus at 12.57 and we were at Giulia's house at 1.19. Found it a bit strange that Giulia insisted that we take a cab. A cab costs around 10 to 15 Euros and we would have to take two cabs since we are 5 of us. The bus fare came to 4 Euros at 1.20 Euro each. Also she seemed annoyed that we could not make it at 1pm to her place as decided earlier. But I think when you are traveling one should make allowances for such delays.
The apartment is good, close to restaurants- especially La Pizza Divina (pizza by the slice and the best ones I have had Italy), you can see it from the window. Supermarket Conad is 3 minutes away as are all the tourist destinations that I mentioned earlier. Even the the bus back to the station is two minutes from the house- Bus # 14C, 14BC 14B. be sure to buy you tickets from the Tabacchi as it will cost you just 1.20 Euros instead of 2 Euros if you buy it on the bus!
All in all a good stay.