How do I know what will be biting when I visit?
Each species in the bay has a season, and the site shows which are running in the current month. Your captain is the best source for the last few days specifically.
Bahía de Banderas fishes all year, but not for the same things. Broadly, the biggest bluewater fishing runs from late spring through autumn, while the winter months bring humpback whales into the bay and calmer inshore conditions.
Use the seasonal guide on the site to see what is realistic in the month you are travelling, then treat it as a guide rather than a promise. Water temperature, bait movement and storms shift the picture week to week, which is exactly why a captain who fishes the bay daily is worth asking.
No honest captain will guarantee a catch. One who does is telling you something about themselves.