Fortaleza Street is the main shopping street, where like in most ports, you'll find the good, the bad, and the ugly...Oddly I found Marshalls there...lol
If you are there on a Saturday, there used to be a flea market right by the fountain in the square near the ships. There are also pushcarts that dot the hill, as you walk up to the mains shopping area. Here's a tast of what you will see.
I did an island tour once I really enjoyed, as it took you around old town, then up to the art deco area, and away from the crowds..
The fort is also an option, but I found it a snooze to be honest.