The National Trust are just completing a new building on the island, not for the Iguana's but for visitors, I also heard there will be new signs to help visitors while they visit this unspoilt bit of paradise. At first it's difficult to see any Iguana's then you suddenly realise they are everywhere, big, small, stationary, scuttling around in ones or twos, if you look long enough your certain to see these cool creatures, there is also a good chance of seeing sting rays off the North shore while walking along the stunning beach, as well as conch and if your lucky a nurse shark. The tour is usually 15 mins or so with the guide and then you can wonder around, it's a great thing to do if you have an hour or so spare.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.