As you will be travelling light, you can take the chance and look for a pensione when u get there. Just make sure you arrive early, not late afternoon when the rooms may have been taken.

When we did this trip years back, we did not have any room booking in Florence. As you arrive and head for the tourist info area, you'll be approached by pension owners offering their place nearby. Check it out if u like the room, and make a deal! That was how we found our pension, which was about a 5 to 10-minute walk from the station.

Oh, and we had our trusty guide book by Rick Steves which I found useful, and easy to carry around.