Lol, I know what you mean Rob.....same thing happened to me and my friend on our very first trip. No one had told us about the departure tax and we literally showed up to the airport will maybe less than $5 each to our names (silly young college kids)
they told us we had to pay the (I think it was like $27 or something like that) and we said we didn't have it. They sent us outside and told us to find the atm. Well it was out of order. We got back up to the counter and they told us to find someone who could give us the money...which definitely is not that easy to do but we must have looked pitiful because a very nice man in line behind us asked what was wrong when he had watched us walk up and away from the line and then he paid for both of us!