Thank you both so much!

I am not sure how this will work out, but I at least want to try to ride SOME of it. If I rode the whole thing, it would be once a week. I used to work with a guy who did the whole thing from Chelmsford about 3x per week. Crazy.

The option that is looking the best is driving to Bedford, then riding from there.
If I map it out on the google pedometer site (http://www.sueandpaul.com/gmapPedometer), it's about 15 miles. I would be trying to come in early and trying to leave early.

SpinSis, I will try to ride that this weekend and to check out the dead end road part. I can't really visualize what happens when you get to Alewife.

Ideally I'd like to get onto Beacon St, to Cambridge St, to 2nd St.