In The Tramp Steamer, Donald and the kids travel south in a little boat. Along the way they reach this little fishing village:
After covering it in soap, they escape. Soon enough, they reach another fishing village; this one:
I was thinking that maybe the first one is Mouseville/Mouseton, as I've seen maps placing it south of Duckburg, and rather close too. We've seen in numerous stories that Mouseville/Mouseton has a harbor, so it should be located on a coast. However, it appears that the people in the panel is wearing sombreros and ponchos, so maybe the intention was that the Ducks had gone all the way to Mexico?
I stumbled upon something while reading The Long Race to Pumpkinburg. The Ducks have an ice skating race to Pumpkinburg, which is located 3 miles down the frozen river. During the race, the Ducks pass Gooseneck Bend. Gooseneck Bend appears again in Boat Buster, where Donald is having a boat race against one of John D. Rockerduck's racers. The race is called Yellowrado River Water Derby, which leads me to assume that the river is named Yellowrado River, and that Gooseneck Bend is a part of this river.
Donald is instructed to take a shortcut "through a tule bog across Gooseneck Bend". While writing this I realized that it says "a tule bog" and not "Tule Bog". Thus, any relation to Tulebug River, Tuleville, or Tuleburg is unlikely... which makes all of this a bit less interesting.
Anyways, we never learn where the goal of the Boat Buster race is located. However Pumpkinburg should be somewhere in between the goal and Duckburg.