When we cruised the Caribbean we always left from San Juan so would stay 2 days before. There are 3 different forts that are interesting. You'll dock by Old San Juan. The town itself is interesting to walk around. But we did enjoy walking around Puerta De San Juan. It's part of the walled city with the big red entry gate. Castillo San Felipe del Morro is a hike up the hill. On the weekends families gather and spend the day flying kites in front of the citadel. We truly enjoyed our stays in Old San Juan. Also there are a few old beautiful churches. I also love the blue brick streets.
Thanks for your post. It made me look up our pictures from that cruise. I can never post pics from pc only from phone otherwise I share a few. Great things to see! Can't wait for your TR!