Spanish is spoken throughout Mexico and Tulum is no different. There are Mayan communities here that are noticeable from their dress and look, but they also speak Spanish.
As a rule most tourist-facing staff will speak English to a degree, you can usually get by with no understanding or grasp of Spanish when it comes to booking rooms, taxis, food or ordering drinks.
It’s not hard picking up a few pleasantaries along the way and will make your stay a lot more rewarding, failing that a shrugging of the shoulders and a polite “Perdon, no hablo Espanol.” will just be just enough.
Either way, to get the most out of your time in Tulum and Mexico, a basic grasp is helpful and will reward you immeasurably as well as making your trip a lot more stress free.