The way points of this bicycle route:
Start out on the Southwest Corridor Bike Path (following the Orange Subway Line) across the street from the Forest Hills Station.
Exit the bike path across from the Parking Garage and go straight thru light to end up on Colombus Ave
Turn Left onto Mass Ave heading towards Cambridge.
Turn Right onto Prospect. Caution, rough road.
Careful, busy rotary and highways.
R on Beachman Street thru Chelsea (this is a rough area with crappy roads and occasional large trucks)
Great flat road with wide shoulder.
Continue Straight onto Beach Street instead of staying on 127 at this point.
Stop here and enjoy beautiful Singing Beach. There are public bathrooms, a snack shack, and beautiful views. You can then either bike back to Boston, or take the Commuter Rail back with your bike.