As a native, I have three words for Boston driving. DON'T BE TIMID. If you're going to make a lane change, make it. Use your signals, but they are not for asking permission around here. They are for TELLING the other drivers where you are headed. If you're taking your Fit, then you'll have fun slicing and dicing.
It's much lower key outside of Route 495. Maine is very low key as far as driving.
The ocean water is probably only going to be in the high 50's the rate things are going by the time you get out this way.
Lots to see in Boston, and if you're here for the 4th, try and see the fireworks on the Esplanade on the Charles River.
And check out the MBTA's website
www.mbta.com to find out public transit schedules and info. MBTA runs the subways and buses in Boston, and the local commuter rail system, which if you are staying in Boston, might be a good option for you to get to some of the attractions instead of driving. It works well, and with the colleges out for the summer, will be easier to use.
PM me if you have any specific questions.