Hell is on Grand Cayman. The taxis are safe. There is some crime on Grand Cayman but it is minimal. Grand Cayman is not a "poor" Caribbean island. The current economy has affected them. Our cab driver told us that they actually had a bank robbery in May. That is almost unheard of on Grand Cayman.
Go ahead and take a cab to Hell, send the post card, look at the small rock formation and buy a t-shirt. That's about all you can do there. It's, at most, a twenty minute stop. Most of that will be finding a t-shirt.