Rome, Venice, Cinque Terre, Naples, Florence

Most people would consider your 5 choices over just 12 nights way too rushed.
Venice (3nts)
Florence (3nts)
Cinque Terre (2nts)
Rome (4nts)
Reconsider Cinque Terre if your travel ends up being after mid October.
Trains are easy and mostly preferable - the Tuscan countryside remains an exception.

With such a very short time frame of 12 days, I agree with David that you're going to need to pare down the Itinerary. Of the five places you listed, which one would you delete first? A few thoughts.....

• I'm not as enamored with Venice as some of the others here, but that's a personal choice.
• Florence is a good place to spend a bit more time, as it's a beautiful city with some interesting sights. It's also a great location to use as a home base for exploring other places in Tuscany (Siena, Lucca, Pisa, etc.).
• Cinque Terre - as you haven't been there before, at least one visit would be good, enjoying Pesto in the area where it was invented or perhaps the Sciacchetrà dessert wine. That's a great place to enjoy "Il dolce far niente"! While it's been somewhat over crowded lately with cruise ship and other tour groups, that shouldn't be as much of an issue at the time-of-year you'll be travelling. You'll have to decide which of the five towns you'd like to stay in (each of us here has a preference).
• Rome has so much history and so many sights, at least a couple of days there would be worthwhile.
• As Naples is important to you, I'd keep it on the list, as the "grittier" aspect will provide a nice contrast with the other places you're visiting.

Do you have any idea yet when in "mid to late 2017" you might be travelling? It would help to have a "ballpark figure".

I'd suggest using open-jaw flights for best efficiency, as that will maximize touring time and minimize travelling time (you won't have to return to your starting point). As you're only going to be visiting larger cities, travel by train is absolutely the best idea. The fast trains travel at up to 300 km/h, so that's much more efficient than a car. However since it's been a number of years since you were last in Italy, and probably didn't use trains as much since you were on a tour, there are some potentially expensive "caveats" to be aware of (that applies with rental cars as well). If you need more information, post another note here.

Good luck with your planning!

Ken, thank you so much for your response! We might have to wipe out Naples -- we can always come back and the last thing I want is to be rushed! We are thinking late September-Mid October 2017.

What are the expensive caveats with the train situation? Looking at the other comment, I am thinking flying into Venice and out of Rome. With the Cinque Terre, what village would you recommend? My husband is an avid fisherman and I would like to get him out on the water at least 1 day while we are there!

And it looks like most people recommend apartments over hotels -- any recommendations there?

Late September to mid October should be about perfect, as long as the weather co-operates. Open jaw flights into Venice and out of Rome would be perfect!

I'll send you a PM with my usual "boilerplate" on the caveats for trains and other public transit in Italy.

Regarding which town to stay in the Cinque Terre, my personal favourite is Monterosso (the most northerly of the towns). It's the largest and therefore has the greatest number of hotels, restaurants and other tourist amenities, and also the nicest beaches of the five. I'm not sure about the statement that "most people recommend apartments", as that wouldn't be my suggestion. I much prefer to stay in a hotel that provides a good breakfast with the room. When I'm on holidays, I am NOT cooking or doing dishes, as I get enough of that at home!!! It's also nice to have staff available to help with sightseeing or transportation information if needed. and nice to have other people to chat with. One of my absolute favourite hotels in all of Europe is located in Monterosso, so I won't be using an apartment there anytime soon!

I have no idea what the opportunities might be for fishing in that area, but hopefully one of the others can help with that.

Ken, I was actually thinking the same about hotels vs. apartments -- I am most certainly not going on vacation to cook either. I look forward to the message regarding travel by train! Thanks again!

Choosing Monterosso can also mean one less change of trains, both on the way in, and on the way out. Most of the faster 'through' trains do not stop at any on the other 4 towns.