We are mid-30's first time cruisers, parents of a 2-year-old, who hadn't been on a vacation in 3+ years, so we were really eager to get away. Our retired parents are all avid cruisers and really wanted us to try cruising as an easy way to get a stress-free vacation. In the end, they were right!
We didn't want to lay out too much cash, so we chose Princess over the Celebrity cruise for the same dates. We went with a balcony stateroom and the cost was about 1/3 of a similar room on Celebrity. We used a local cruise agent (who booked us the exact same cabin I had seen available on the internet, but also got us $75 shipboard credit, so that was something).
We flew down the afternoon before departure and enjoyed an evening in Old San Juan. Our hotel was the Sheraton San Juan Hotel right near the Pan American Pier, very convenient. Could have easily walked from there to the ship but for our bulky luggage, so we took a cab (about $7).