This was my 3rd cruise on Carnival and 5th overall. We're in our mid-40's, and keep coming back to Carnival as we love the "fun" factor that has been lacking on other cruise lines we've tried. I sailed an identical itinerary on the Victory a few years ago w/my daughter, and wanted my husband to experience those same ports. This was a Valentine's cruise for us.
We sailed out of San Juan and spent one night pre-cruise at the Posada San Francisco hostel, right in the heart of Old San Juan, about 6-7 blocks from the Carnival pier (a relatively easy walk on the morning of the cruise, even with a couple of wheeled suitcases). This bare-bones hostel is clean and secure and offers of a few rooms with queen beds - plus there's gorgeous view of the port from the upstairs lobby/balcony. I read about this place on Cruise Critic and stayed here a couple of years ago as well. No frills, but we also didn't want to be out a whole lot of $$ if our flights had been delayed (and if we missed our reservation). Highly recommended due to location and low-cost. Easy walking distance to everything in Old San Juan, only about a block and a half to catch the free trolley.
Embarkation was easy-peasy, we signed in and dropped our luggage around 11am, then spent the day walking around Old San Juan and El Morro. Walked onboard around 5-6pm, all luggage had been delivered and the cabin was immaculate. We booked one of the "Scenic Grand Oceanview" cabins at the very forward corner of Deck 9 (just above the bridge)... LOVE AT FIRST SIGHT! A huge, oversized cabin with floor-to-ceiling windows and electric blinds for at night - the blinds must be down to keep your cabin lights from interfering with the bridge/navigational cameras. These cabins are the next best thing to a balcony, and with 5 ports in 7 days you honestly wouldn't have time to enjoy a balcony anyway.