I politely told them I lived in the north and could not come back in 45 days for the driving test, they said Ok come back tomorrow... I did and left with my license.
That type of good fortune doesn't find me very often. Since I wasn't going to SD, I went to Puerto Plata. While a pain to go back 45 days later, it's a fairly quick trip down the street from Sosua so it wasn't too bad. Getting the license within a few minutes of completing the practical test, without having to go back later, not being asked to produce yet another document and without having to fill someone's outstretched hand was satisfying for this newly arrived person. That success was exactly what I needed at the time.