To get to Tulum, most people fly into Cancun Airport (CUN), which is about 2 hours north of Tulum. You can also fly into the beautiful island of Cozumel (CZM) and then take the boat ferry over ($12, 40 min). Then take a shuttle/bus (ADO) or taxi down to Tulum (45 min).
Make sure you find out the going rate and then tell the taxi in Spanish how much you are paying him/her for the ride, otherwise you may get taken for a ride.
The bus/shuttle (ADO) is a great deal and comfortable. For around $12, you can go from Playa Del Carmen to Tulum. If you take the Ado from Cancun, you will need to stop in Playa Del Carmen and transfer bus.
It’s always better to pay in Pesos that any other currency to get the most out of the exchange rate!