Do I need to know Spanish?

It is beneficial to know some Spanish when traveling in Mexico, but it is not strictly necessary.

Everyone you likely need to interact with at the resort will speak in English with you. Some of the staff are more basic in their English and you can't venture too far in English with some, but bartenders, event staff, and management all have an excellent command of English. The only place that can be a bit intimidating is the Customs officers at the airport can have very thick accents and may not speak English fluently, but they are generally patient and are trying to move you through the process quickly.

Learning some basic Spanish phrases can enhance your experience and help you connect with locals and the international staff as well. It shows respect for the culture and can make interactions smoother. They show respect back with stiffer drinks and joviality.