I was in the same position as you are, except Ive decided to get my open water before traveling to my destination.
The difference between the resort course and full open water is that a resort course in no way makes you a diver. You will learn only enough to get by with a certified instructor by your side, and not enough to get into trouble.
Each resort may require you to take their course. There is a PADI scuba course that allows you to dive with an instructor, and this may be accepted on your dive at other places.
If you arent at all certain you want to dive, and you arent familiar with the water, I see no harm in taking the resort course. Youll get in one dive, with a guide, and you can determine whether this is for you or not.
The one warning I would give is check out what the instructor to student ratio is. Obviously, the lower the better. If something goes wrong, even something that appears minor, the instructor has to respond, and the rest of the group is temporarily on their own. With six uncertified divers and one instructor, if two divers have simultaneous problems, someone goes without help, or the experience to know what to do.
This in my opinion is the biggest drawback of the one dive courses. You dont have the experience or training to handle any type of problem.
The better the course instructor, the lower the student to instructor ratio, the safer the dive will be, and likely more fun.
Just be sure to check out the course in advance.
Xanthro