Now that I know better where you hang your hat, I'd go with taking Route 4 in to 128. You'd probably have the easiest access to 4 from Treble Cove Rd; it's a two-lane highway that traverses the southern portion of Chelmsford and then cuts through a corner of Billerica and across Bedford before meeting 128 near the Lexington line. Not too many stoplights (we call 'em "sets of lights" around here lol) and traffic backups aren't all that bad. When I visit my "transplanted" friends in Chelmsford it's about 15-20 minutes from 128 to Treble Cove Rd. But that's on weekends and holidays obviously. For a commute like this past Friday's I'd allow closer to 45 minutes door to door. (You'd spend next to no time on 128 south from the 4/225 interchange.) Commuter rail would not be realistic.
Another lingo tip: No New Englander puts "the" before a route number

Did you live in California before? LOL no worries!