We did Italy last fall, the advice you have gotten so far is spot on. Naples seemed a bit sketchy, but for a day or two I guess it is fine. We ended our trip planning on touring the Almalfi coast, using Sorrento as our base for 4 nights, we loved it so much, we only did Capri and spent the rest of our time in and around Sorrento. The trains are definitely the way to go. We started up north (Milan to Venice to Cinque Terr to Florence and then Rome, using trains for most of the legs of the trip. Wonderful experience, don't worry about the language barriers, you will be fine.