The transportation that goes to MK should start about an hour before MK opens. However, since that CR boat doesn't go to MK, it might not be running as early as the MK boats. Even it was running, this is a trip I'd
budget at least an hour for.
However, and I'd check this with the bus drivers, but WL buses going to other parks besides MK "usually" stop at the Poly, GF or both en route to the park. Ask your driver to make sure, but this is by far the quickest non-taxi way to get from WL to Poly. Getting back TO WL from Poly: monorail or boat to MK, then boat back to WL.