Yes. Several places are cash only. We recommend exchanging cash for Pesos at the airport or prior to traveling. There are ATMs in town.
There are several golf cart rentals in town. However, everything is walking distance. (KALiVA Sayulita is a great place for rentals) Transportation for events will be with taxis in the main square. Transportation to and from airport (https://www.sayulitalife.com/taxi_transportation)
Comfortable walking shoes. The town is cobblestone streets, so shoes that are easy to walk in. Wedding venue and polo match are both on grass. Passports!
If you have an international plan, you will be good. Download WhatsApp to text and call in town. Most places will have Wi-Fi to connect to as well.
Fly into Puerto Vallarta (PVR). Sayulita is about an hour from airport. (Use transportation service at www.sayulitalife.com)