We just got off the 7 night Southern Caribbean on Sunday. We loved exploring Martinique on our own. It really was unlike any other caribbean island we've been to before. Tons of shopping right by the ship & even a fort nearby. It was really cool just know that the language is French & they take the euro, though most places had signs saying they take the USD. Old San Juan is also extremely doable on your own- you won't have an issues with language or finding the sights in Old San Juan. Barbados is big on snorkeling with the turtles if you're into that kind of thing. The port area seemed kinda sketchy once you left the initial area so I would probably go with an excursion there. We took a cab to the Hilton for the day. St. Lucia is great for snorkeling and/or visiting the volcano/mud baths/hot springs/waterfalls- that area is about an hour from the ship & is either accessible via water or car. If you are a nervous rider or prone to car sickness, I'd take the boat transportation. St. Kitts we took a taxi to the Marriott which was really nice! We didn't visit Aruba so I can't help you with that one.