It's the Ticketing and Transportation Center up by the MK parking lot - next door to the Polynesian resort and right by the monorail station - if your not at a MK resort, the best bet is to get the bus to MK park and then the resort monorail or boat (to either Polynesian or the big ferry to the MK parking lot). You could also get the bus to Epcot from your resort and get a monorail from there.