We had Labadee changed to Grand Turk for our April 12th sailing - it took 2 weeks before we could see shore excursions listed for our cruise, but we were able to change the app to look at other sailings prior to ours to see what was offered on theirs. You may have similar luck by switching the sailing dates in the app and looking at one that is going to Puerto Plata to see what is offered as shore excursions.
We were in Puerto Plata last week. We did the Isabel de Torres excursion that also included a city tour. It was really enjoyable. The ride up the mountain was beautiful and our guide (Pedro, aka Kappy) gave us a lot of information about the town, country, and the mountain. It was cloudy so the view was pretty much non-existent, but the national park was still very nice to tour. The city tour part was actually okay because Pedro knew his way around and was able to get us into the souvenir shop when it wasn't crowded, and also onto Pink Street and Umbrella Street when it wasn't slammed completely with tourists.