If DHS is still open, you could also take the bus to DHS & transfer there to the bus to Poly. The ride from CBR to DHS is under 10 minutes, and Poly is the 1st stop on the bus from DHS to Poly & GF. Travel time would be about the same as transferring to the monorail at MK.
I would take whichever bus comes first, MK or DHS.
But avoid going to DHS a few minutes before closing; you don't want to run into the exiting crowds.