Punta Cana to Bayahibe by bus
By guagua involves multiple bus changes. You need a taxi to get from your hotel lobby to the bus station at Fruisa. From there take a guagua to Higuey (45 minutes). From Higuey take a guagua in the direction of La Romana. Ask the driver to drop you at the Bayahibe turning (40 minutes). From there take another guagua into Bayahibe (10 minute ride) these come from the direction of La Romana.
Hot n sweaty bus journey, be prepared to wait in the sun (no shade at the Bayahibe turning).
On the return journey once in Higuey you need to get to the Punta Cana/Bavaro bus terminal. Sorry, not sure if the bus stops there.
map of Higuey showing bus terminals
Take the bus to Bavaro, not Punta Cana (that one goes in the direction of the airport). Get off at Fruisa bus station (or Steve's corner bar if the bus stops there) and take a cab back to your resort.
map of Fruisa bus station + area round your hotel
A taxi from Punta Cana to Bayahibe will cost around 110$US one way...