In all the times that we have been they have never once asked to see ID. The transport is for anybody to use if they have a park ticket and I suppose given the volume of people, the majority of which will have park tickets, its just not worth checking and holding up the lines.

As PP just said, you will have to get to a resort to catch a bus to the park. If you're not in a rush, walk to the boats next to the Rainforest Cafe and catch it Port Orleans French Quarter or Riverside...its a lovely way to travel on the river cruise. Again you won't get asked for ID and even if they did you just show your park tickets...then just hop on the bus there