There are NO buses to the Boardwalk at the Transportation & Ticket Center.
All Disney Resort Transportation is based out of 5 Hubs. Those hubs are the four theme parks, and Downtown Disney. Just like any city transit system, you need to connect at a Hub to get to some areas. Which hub you use, is up to you.
To get TO the Boardwalk...
1.) Catch the Monorail to the MK, and then connect to the Boardwalk bus
--OR--
2.) Catch the bus to the Studios, and connect to the Boardwalk boat.
To get back to the Polynesian:
If either theme park is still open, reverse your steps. Otherwise, use Downtown Disney as a connection point.