I was there back in the 70s. It is a beautiful island. I don’t remember that there were a lot of good roads but if you have a beater bike or a mountain bike, I would take it. I don’t think I would take a high dollar bike.
As for the brown snakes, they are nocturnal and I hear they are everywhere after dark. They get about 9 feet long and are slightly venomous something like a bee sting.