I did the same from Providence. Parked in the mall and walked over. The garage there sucks. I found that taking the commuter in the morning and Amtrak at night was best. In the morning, if you miss one (traffic, etc), there will be another one rather quick. With amtrack, you've got one shot, so to speak. Also, with Amtrack, you can book a few weeks ahead and save big bucks, cancel if you have to, and they add your fare back to your account. Used to take the 5:30 home.