Below is a taxi fare zone map for Playa Del Carmen. It states fares that are correct. If you need a cab, hail one from the side of the road, know the fare and pay upon exit. DO NOT ASK HOW MUCH. Tipping is not customary, but you may tip if you wish by rounding up to the nearest peso amount.
If you pick up a taxi at one of the taxi stands, it will usually be more expensive. Try to avoid them completely. Very often, taxis will avoid picking up locals to pick up tourists as they often can charge a higher fare as tourists do not know the correct fares. With this map, you can save money and help locals who need to use the taxis as well.
Below is a taxi fare chart for Puerto Aventuras. It states fares that are correct. Tipping is not customary.