Ellen,
My experience has been similar to what Michael mentioned. If you do manage to find a free Wi-Fi Hotspot, it may be overloaded or very slow.
Depending on what Hotels you'll be staying in, an increasing number these days offer Wi-Fi service (sometimes at a small charge). My position is that I'd be paying to check my E-mail or whatever at an Internet Cafe anyway, so paying a small charge is not really a big deal. It appears that for the most part "there's no free lunch".
One other thing to remember is that Italy has enacted some very strict anti-terrorism laws, and anyone using "rented" internet access is supposed to be "registered". If you use a Net Cafe, this will most certainly be the case, and they will ask for your Passport. I haven't used Wi-Fi a lot in Italy, so I'm not sure what the policy is on that?
I'm travelling with an I-Pod Touch these days, so will be in much the same position in a few weeks. I'll have a better idea and more specific information on Wi-Fi access when I return.
Incidentally, someone posted a link to a "Wi-Finder" here on the HelpLine recently - check This site for details. One caveat though, that site gets "mixed reviews" at the Apple App's store.
Happy travels!