Don't know how long you're going to be in San Juan, but we visited Arecibo Radio telescope which is the largest telescope in the world. It was featured in a James Bond movie with Pierce Brosnan. Very nice trip and tour. Awesome. We also went to Camuy Caves which are home of some of the largest underground caverns. Look on the Puerto Rico website and they will send you free brochures and books. My book is called Go To Puerto Rico Travel Planner. has hotels, things to see, etc. Was very helpful in planning what to see as it's sectioned off by geographic location N S E W and you can judge how much time things will take. We were in SJ 2 days prior to cruise which was cool. Have a great time.