I think the shortest trip would be to go to HS and switch to the PO bus there. Of course, the park will have to be open when you do this. Going to Epcot would be another, similar option.
Going to DTD would not be a good idea unless you plan on staying there for a while (Something to consider). When the PO bus leaves DTD it does RS first and then stops at FQ last while the HS and EPCOT buses stop at FQ first before RS.