I was there on the Sapphire Princess about 3 weeks ago (great ship, great cruise BTW). It would be about a 30 minute walk each way to town, I would not suggest that. There is decent size building at the port, about the size of a Walgreens, with various souvenirs, all about double what you pay in town, but it is right there and you do not have to go through security or anything (other than on the ship). They have shuttles right there, they take you to town for 3 bucks per person, and bring you back for one dollar. It drops you off right in the middle of town, by the town square and some pretty decent shopping. I actually found the shopping better than Cabo, which was WAY overpriced. It gives you a taste of Mexico. I too thought it would be a throw away dump, but it wasnt that bad. There are winery tours, and the blowhole (tourist trap). Right at the port, there is your standard variety of mexican souvenirs. Here is a great video, you can see exactly what there is. The nice things about the port shopping is no beggar or children pushing candy This video gives you a decent idea. The building at the port has just about any typical souvenirs, there is just much more choice and cheaper prices in town. Is there something in particular you are looking for?
https://www.youtube.com/watch?v=KRCuq8zVFLc