Excellent. Some great info.Boston is a great little city--much more like NY than Florida.
Here is a link to the train to Portland. Looks like it's about a 2.5 hour ride. Looks like a beautiful ride and I definitely recommend Portland for a night or two if you want (select a hotel in the Old Port).
A car is definitely not necessary, especially in Boston. The Freedom Trail is great--my suggestion is start in the Charlestown Neighborhood with the Bunker Hill Monument--you can hike to the top of it. Fenway tours are great and they take you up on top of the left field "green monster" wall which is awesome. The Celtics will be in season at the end of October and beginning of November, so a game would definitely be doable (Oct. 30 vs. Wizards), (Nov. 4 vs. Bulls).
Cambridge is not technically Boston but it's where MIT and Harvard are and they are worth a walk around. Harvard Square should definitely be on your list.
In Boston, don't miss the Common and Public Garden. Faneiul Hall is very touristy but a walk through the food court in Quincy Marketplace is a must. I really like the Back Bay/South End just past Copley Sq. The South End, in particular has some of the city's best restaurants. The area around Fenway Park has been built up over the past few years as well as the Seaport (However, they don't have the "old" feel that the rest of the city does). I think the "Duck Tours" are better than any of the sight seeing trolleys you might encounter. You get a tour through the streets and then the truck you are on turns into a boat and you get a tour on the Charles River. For a great meal you have to go to Boston's Little Italy, The North End. There are so many great choices there, but after dinner (or any time!) you have to hit either Mike's Pastries or Modern Pastry for cannolis. Mike's is take out only but you can sit down at Modern's and get an espresso as well.
Hopefully this gives a little insight!
I had a look at Portland and the Amtrak route from `Boston so will definitely do that and stay for at least 1 night.
Much appreciated.