I don't know when your cruise is, or if you've already taken it, but if you haven't gone yet, I can help. First of all, as for the shopping at the cruise terminal, although "duty free", keep in mind that convenience is expensive, and this was built for the "convenience" of the cruise passengers. Just walk right on through this area. Take a cab (less than $5) to "El Centro" or downtown. There you'll see many shops and great restaurants. However, again, those on the main street, and air conditioned, are going to be more expensive. Walk back into the mercado (market) about 4 or 5 blocks. When you no longer see air conditioning, you've entered the right place to shop. I couldn't believe the difference once I was given that advice. There is now a little jewelry shop we visit every time we go, and the owner even remembers us, gives us incredible prices, throws in free stuff, etc. he so much appreciates the business. His sign says "THIS IS THE PLACE"! lol
Good luck and have fun!