you coudl also take a look at Boston's BIke Map (http://www.cityofboston.gov/TridionI..._tcm1-3455.pdf).

a quick peek suggests that Mass Ave to Dorchester Ave would work as long as you can take the traffic. personally, I've had enough close calls on Mass Ave that I avoid it whenever possible.

depending on where in Cambridge you're coming from, you could try Ruggles to Warren to Talbot.

good luck and also check in with the friendly folks at bostonbiker.org!