I don't have experience renting from Alamo or arriving via cruise, but $19 seems way too low. That fact and the bad reviews would have me thinking twice for sure. Kennys gets awesome reviews on this board and I've used them before--not exclusively though. If Leslie at Kennys has can recommend a friend, I wouldn't hesitate for second. Don't make the mistake of ruining a day on the island in an effort to save a few bucks. It could really taint the rest of a wonderful cruise. Oh, I agree with Carol and Scuba--rent at the port. The time and hassle getting to the airport is not worth the relatively minor savings.