Uh, the Sox won't be playing in March...they'll still be in Florida!
I just answered a similar question so let me share that answer here as well...
There's a great club scene on Lansdowne Street (adjacent to Fenway Park).
Like any city, parts of Boston are safe at night and others are not. The Theatre District is fine when there are shows at the theatres, but it's unfortunately near what's left of the "Combat Zone", the adult entertainment district which is shrinking over time, but is still pretty scuzzy with hookers. Faneuil Hall Marketplace is the "tourist trap", but the food choices are endless (and no Boston visit is complete without a meal at Durgin Park). The Comedy Connection is a great night out.
Boston is a highly walkable city by day because everything is so compressed. But the streets are not laid out in a grid so the walking can be a little convoluted...be sure to have a walker's map. The MBTA (subway and buses) is reliable. I'd avoid the cabs unless otherwise stuck.
Places to visit: If you like to shop, Newbury Street is the place to be. The Museum of Fine Arts and Museum of Science (Cambridge) will suck up the better part of the day. If the weather is good, plan a few hours for the Arnold Arboretum ("The Arborway") for peaceful walking. Good walking also along the Esplanade of the Charles River from the Harvard bridge to the Hatch Shell, again if the weather is good.
History buff? Take the Freedom Trail walk from Boston Common. It's a self-paced trek.
Baseball fan? Take a tour of Fenway Park. Inexpensive and a lot of fun.
Italian food? The North End has the BEST in the
USA, and I'm not kidding. You have to go to Italy to get better and more authentic.
Just outside the city proper is the Bunker Hill Monument. You'll need a couple bus rides to get there.
Harvard Square is a bustle of activity...shopping, food, history. Another highly walkable area.
And here's a tip to help you find things to do and see: take a ride on the Duck Boats. It's a good way to get a feel for the city, and the tour guides tell you what's worth exploring in more detail.
Oh, and Shelby is correct: if you're around for St.
Patty's day, take in the parade that Sunday...but don't wear a NY Yankee hat if you value your life (-: