The Polynesian is centrally located. You can take the monorail to the MK, or ride the smaller boat launch shared with the GF. The TTC is next door, so you can walk over there and take the Epcot monorail. It's the only MK resort with such direct access.
I highly recommend you walk instead of taking the monorail to the TTC since you will go all the way around the lagoon, a trip which will take 20 minutes: nice if you're not a hurry, but not so nice in the morning. If you stay in the Rapa Nui, Tahiti, or Tokelau buildings it's no more than a 5 minute walk to the TTC.
To get to MGM, AK, DTD, or the water parks you take a bus (shared sometimes with the GF).