Grenada I would look for a private guide if you want to see the island but you can just walk around St George's or take the local bus ...they are mini vans & drive around the streets picking up people ..just tell them where you are trying to go & they will tell you if they are going that route.
Some charge a different price for tourists but some don't
Dominica you can probably get a tour at the dock we took an island tour with a local taxi guide (Campbell) it was $75. USD for the 2 of us. We could not find others to share.
Just do some research to know what you want to see
Alexandr Pushkin, Carnival-Holiday, HAL-(old)Westerdam, Orient lines-Marco Polo, Royal Olympic-Olympic, NCL-Dream, Dawn-Princess, ACCL-Grande Caribe, Oceania-Insignia (3), Regatta(4) Marina (1) St Lawrence Cruise Lines-Canadian Empress
Scenic River cruise June 11,2012