Finding accommodations

Yes you can. I've never had problems finding places on the fly, except for Venice some times and Rome around the end of April (2 national holidays on 4/25 and 5/1).

However sometimes you might hit a few places with no vacancy before you can finally find a place with availability. I often travel on the fly in Italy, generally booking the day before or even the same day. In the old days, before Internet, I would have the list of all hotels (from Enit, or the provincial agencies) in an area, then call until I found availability. Sometimes I would simply walk in and ask. Generally, even on a bad day, I would never have to call more than a handful of places before I found a vacancy. Nowadays I do a quick search in a hotel search engine. That is much more efficient because you can sort by price, location, etc. If you have a car and stay out in the countryside or smaller, you won't have a lot of problems finding places with vacant rooms, even if you walk in.

If you stay in Florence at any time, I would search a place in Florence ahead of time at least just for the days you know you are in Florence. You will certainly find places on the fly, but by looking ahead you can get the better places. Florence is packed with tourists in May.

Yes, I booked all my rooms on the fly in Tuscany and Umbria in first half of last October. In Pescara, Deruta, Gubbio, and Rapallo, I did not have any listings in hand and just showed up in the afternoon and found a room. In Montalcino, Volterra, and Lucca, I called or emailed not earlier than the evening before arrival, using listings in Rick's Italy guidebook. (Email is not the best method for last-minute bookings, since you have to allow time for a reply. Not all online booking engines work with an equal level of immediacy, either, so read what they promise.)

You can also check a booking site (booking.com is the one I use) the night before or the morning of your arrival in the next town, so you don't waste time looking for a place.

suzie,

Mid-May could be busy in Italy as that's "spring shoulder season", so having pre-booked accommodations would provide you more choice in terms of location, price or comfort level. However, you should be able to find something, but may have to take what you can get.

Yes, you might want to check Bookings.com now and see how availability looks now, if you are not picky about private baths and room arrangement you will probably be OK. I know when we booked rooms a couple months ago for mid to late May I did run into problems getting two rooms. I am feeling this is a busy time of the year before summer travel.