We booked this tour through our hotel. It was a 3 hour guided bus tour of the whole island. It stopped about 6 times at various spots around the island, including the blow-hole, Morgan's Cave, the first Baptist Church up on the Hill, a house that was restored to be like it would have when the island was first settled, among other stops.
It was a great way to get our bearings of the island early in the trip, and only cost $20US and drinks were included!
You can hire abike, it is very cheap and you will not need more than two or three hours to go every where on the island and even hava a swim in La Piscina and go to Morgan's Cave