Hi,
We just returned from the Wonder 3/24 cruise, and we rented a car in Freeport. Weird thing - they drive on the left side of the road (like all U.K. countries) but the cars are American configured (steering wheel on the left!). This is hugely dangerous (to me) when you want to pass! If you don't have a spotter (passenger in the front seat) you have to pull completely out into the oncoming traffic to see if you can pass! Also, if you are not comfortable with left hand driving (roundabouts etc.) I wouldn't suggest learning in the Bahamas.
Our driving tour was a mistake. What the brochure described as "quaint villages" turned out to be shanty towns. Don't kid yourself - Bahamas is a third world country, and you could be in trouble if you're not well informed or careful. The best sights are probably the major attractions, but I'm not sure about Nassau (we did the Dolphin thing that day). Good luck. Hope this helps.