POP area
Hi Vegas. I can't speak for Punta Cana as I have never been there but in the POP area, when standing on the side of the road you will easily be able to figure out what is what. You just stand on the side of the road for the direction you want to go in. You will recognize the public taxi's because they will have cabarete - POP or Sosua - POP or some sort of sign on top saying where they will take you. They will drop you off at any location along the way but do not normally venture off their normal path. When you get out and still need to go somewhere down a side street, etc., just grab a motoconcho to take you the rest of the way.
The guaguas are little minivans (they usually look like a VW type van) with tons of people crammed in and a guy hanging out the door who takes your money and helps pack in the people. They are lots of fun but DO NOT keep any large amounts of money in your pockets as I once got pick-pocketed (only 400 pesos but still)!