Public transport-Puerto Rican style

Let me tell you how surprised I was to see so many fast food restaurants in SJU airport.
Not one to be easily impressed, but I wasn't expecting fast-food culture to have dominated the island, the way it did. But hey, here I was, just after a huge burger when I heard the shouting on the road accross the restaurant:

Publico!! Publico!!!

I heard someone shouting next to a big white van. I was as intrigued as I was confused.
Is it because I just endured such a long flight? Or is that guy trying to sell his van right here at the airport? Is he calling people to see his van?

Hold on a minute, there a few of these, but none of them are shouting like this guy. Well my friends, after some explanation, I finally understood it myself.
Publicos are a form of public transport. Think of a bus like the ones we have in Europe, have you thought about it?
Ok, forget it. Publicos are indeed the closest Puerto Rico has to a bus, but this sure ain't a double-decker.
Publicos are vans, usually a 8-seater, that have a pick-up point and a drop off. There are several companies and many of them cross the island. I am paying a tribute to the publico drivers because without them, many people without a car would be literally stranded.
Public transport (subway and bus) are only available in certain parts of San Juan, meaning an incredible amount of cars and traffic for such a small island.
An investment on public transport and railway connecting the big cities would be welcome!!!

P.S- The driver was trying to get a few more customers. Something not normally seen at SJU, I was later informed.