Rome to Salerno in 3 weeks

If you say you can do Rome either at the beginning or end, I think it's about the logistics and whether you want to fly out of Roma Fiumicino or Napoli Capodochino. I've flown out of both and definitely like Naples better, but you can't get a nonstop to the States from there. If Rome is indeed going to be the departure point, tag it on the end of the trip. And add a couple days there too. If you have 3 weeks from Rome to Salerno, spend a week in Rome.

The other 2 weeks? This is really an opportunity for you to tour southern Italy, visit places not usually seen. Certainly spend 5 days or so on the Amalfi Coast and chill. Sorrento is the best base, Ravello is the most beautiful spot. Fall--depending on when in fall--should be a little less hectic than high season, thus more enjoyable. Then, I would spend a few days basing in Salerno, where we booked 5 nights in the Old Town at a B&B and used public transport to Naples, Amalfi, Pompeii, Paestum, all under an hour each way & cheap. Really enjoyed the small city vibe in Salerno--less expensive, better food too, I think. And it's a great way to easily see the ruins on a day trip. Do not miss Pompeii. In the fall it shouldn't be hotter than Hades, and it's just plain fantastic. Paestum a little south of Salerno is great as well.

Heck, you'd even have time to take a couple days and visit the caves at Matera in the province of Basilicata. I've never been there but heard it's breathtaking and very cool besides.

I haven't mentioned Naples, which gets kind of a bad rap sometimes but can be immensely rewarding. If flying out of there you might want to finish up your trip with 2-3 days there to get the flavor. Do your research though to find the right area in which to stay.

Enjoy your planning!

What Jay said, except I would spend a few nights actually on the Amalfi Coast.

Jay, Matera is one of my favorite places, I go back every year. Big local celebration the first week of July.