I'll comment about Dominica since nobody has. First, don't bother with the ship's excursion for this island. You can find something cheaper outside the ship exit to town. Lots of people will be coming up to you, inviting you on their excursions. Most of them have picture books showing you where they'll be bringing you. From memory now, there're a few places to visit, but I recommend Emerald Pool. It's about 40 mins drive up to the mountain and at the entrance ($2), you walk an easy path through a very nice rainforest. Very easy walk. At the end of the trail, only about 20 mins if you walk slow and enjoy the pace, you'll come to Emerald Pool, with waterfalls. When we were there, the pool was about 3-5' deep, cool and relaxing.
There's Middleham Falls for the more adventurous, and I believe is a more spectacular rainforest trail to the falls, but it's a 8 mile uphill, pretty intense.
Tralfalgar Falls is OK, but the walk is muddy and dirty when it rains (bring a raincoat, it rains alot in these interior rainforests)
After our emerald pool visit, the driver, drove us past the botanical garden, not much here, and then up to the Morne which is on top of a hill overlooking the harbour with ships, etc.
All in all, it was about a 4.5 hours trip and we paid $15pp. (there are also $40 ones, but don't go for the first person who ask you.. quite tempting, since ships excursions are about 60) Good luck.
