ATMs and banks are easy to find in Tulum. There are several right on Highway 307 in the middle of the village.
Credit cards are accepted at larger hotels and a few of the restaurants and stores in town but don’t be surprised if they add on a 5% bank charge to your purchase.
There is a large San Francisco Asis supermarket on the corner of 307 and the Boca Paila road. It’s on the Coba side of the highway.
There are several nice cenotes close enough to town to ride a bicycle to. There will be a small admission charge but swimming or snorkeling in a cenote is a pretty cool experience.