... bicycle helmet laws are bad for my health - & yours too!
I have cycled in Florence, but mostly merely walked there as the city centre (even outside the highly-touristed area in the microcentro) simply isn't very large, but I was being a tourist and visiting Florentine friends there (I was studying in Italy, first in Perugia, then in Rome). Indeed there are a large number and wide range of cyclists. Since the centre of Florence is flat - and also because theft IS a problem - a lot of the bicycles are reliable old beaters. I wouldn't suggest leaving a bag with money, documents, a computer or other valuables in a front basket, as lo scippo (a noun of Neapolitan origin, but now known throughout Italy) is an Italian speciality. It means "ripping off" while driving a scooter (I'm sure it is even possible on a bicycle). I hope you found nice places to stay and eat in Florence - it is so heavily touristed that ripoffs are common. If you know people there, such as cycle chic colleagues, that can be a big help. I remember staying here once, at this hostel in a lovely old villa, between Florence and Fiesole, in the hills surrounding the town: http://www.ostellodifirenze.it/index.asp Have no idea of current ratings (prices are still very reasonable, according to their site), and they hire bicycles. That can be a good solution for travellers on a tight budget.
Thanks for all that info, Lagatta! - might look into your lovely old villa next time...because there is so definitely going to be a next time - LOVED FIRENZE!