From the Airport:
Exit the airport, go left to the main street and you'll find a bus stop right in front. Look for a blue old school bus with the sign 'CENTRO' on its windshield. The bus will take you downtown. Whenever you see the boardwalk (you'll see the ocean and some statues) on your right, push the button to request a stop or just tell the driver to stop (in spanish "Baja"). You can also tell the driver to take you to the 'Malecón'. Once you get off there, we're only one block to your left referring to the direction the bus is going. (costs: around 8 pesos)
From Sayulita:
Take a bus to Puerto Vallarta (costs: 42 pesos) and get off at the very last stop. Here you have to change to one of the old blue school buses to the 'CENTRO' and get off at the 'Malecón'.
By walking:
DO NOT WALK! It's too far... :-)
Calle Juarez 535
Puerto Vallarta, Jalisco 48300