I went to Dominicia on Carnival's Fascination. Not to sound negative - but I wish I had stayed on the boat that day. We took an island tour and it was a waste of money.
It is true - it is a very poor country. After the tour, I went walking nearby and went into a grocery store. I felt that I was walking into a store from the 1800's. They do have a Kentucky Fried Chicken near where the boat docks but otherwise - it is the poorest place I have ever been.
The Emerald pool, Trafalager falls and the plantations were nice to see but it was definitely not worth the $40 cost of the island tour.
The island is not possible to tour without an excursion and in my opinion -the excursions are not worth it.