ask the locals .. someone who works where you are staying .. someone your shopping for something else with just say your looking for batiks or cotton fabrics and they will help you. I found the people in Mexico were warm, charming and helpful. Good luck. I think one can only snorkel so much or suntan so much. I would rather bring a piece of fabric back than a dumb tshirt to be sure
a real memory. I also went to the ruins, explored ancient buildings and swimming with sea turtles. There is time to do a whole lot I think. Most excursions are only 2 to 3 hours so your on your own for enough hours to eat lunch out, explore a bit and well shop for fabrics if you want to