I'll second what CarolMN said.
SSR is a huge resort, and the bus stops there are at least a 15-20 minute walk away from any part of DTD (there are actually two walking paths, one that goes to the West Side near Cirque, and one that goes to the Marketplace near the Marina).
You can certainly try the boat from POR or POFQ, but those boats only run after 4pm daily, and they take at least 20 minutes to make the trip - more, if they make multiple stops at both sides of Port Orleans and at SSR.
You r best bet when travelling via Disney transport is to take the bus to CSR or CBR, which are both located just off West Buena Vista Drive in a direct line between AK and DTD. The Pop Century bus would also do in a pinch; Pop is on Victory Way, a short distance off WBV Drive, and is between AK and DTD. CSR would be my first choice since as a convention resort it seems to have some of the best bus service of any WDW resort.
If time is a factor, then a cab is your best bet.