Ciao Beth and welcome to the DT forum!
Traveling alone should not be a problem, just follow your own common sense as in other countries and avoid taking less-trafficked streets after dark. The centers of Rome and other main Italian cities have a lot of pedestrian traffic in the evenings so stick to these streets and you should be alright. After dark, I'd avoid the side streets alongside Termini station in Rome and Centrale in Milan and similarly in other cities since they tend to not be the nicest areas in town.
Depending on how many days you will have, and if this is your first visit to Tuscany, then I definitely suggest you spend at least 2 days in Florence. It is a beautiful renaissance city with a lot of artistic and architectural masterpieces. See our site dedicated to
Florence for ideas on what to see and do. Then make your way to
Siena, a wonderful medieval city, so that you can see another side to Tuscany.
Traveling by train to all of the main towns in Tuscany is really easy. Depending on the time you have, I also recommend seeing
Lucca, whose original walls around the city still stand. And if you can, the
Leaning Tower in Pisa is a must-see, too.
Hope you have a great time on your holidays!