From POR, you can take the bus to all the parks or a bus or boat to DTD. (Boats don't run as long as the busses do).
You can NOT get to the parks directly from DTD.
was just there last week. it was beautiful. it was my first time at the pors. we always stay at shades of green. the bus service is great, i even let my 18yo dd and her friend go off on their own. they had no trouble at all. have a great trip.