First, this was the Carnival Valor repositioning cruise from 3/22/15 out of San Juan arriving on 3/27/15 in Port Canaveral. Therefore, we only went to St. Martin and then St. Thomas with 2 days at Sea. As a result, the cruise price was insanely cheap.
We arrived a day early at San Juan just in case our flight was delayed. Spent the night and the next day arrived at the San Juan Port. The Port was pretty nice and clean (compared to other port areas I've been in). Staff were friendly and we had purchased Faster to the Fun, so there was no wait for us in line. Because we were there early, we had maybe 20-30 minutes before they started boarding the ship. Boarding went smoothly, we found our room (Empress 7423 Balcony) and dropped off our bags (our other luggage had not yet arrived), and got a bite to eat in the Lido Deck (Rosie's). Room was very clean and the bathroom was immaculate, although shower was a little smaller than I'm used to, but the shower curtain gave you some extra room. Water was ALWAYS hot and plentiful. Only downside was the ancient CRT Televisions Carnival still uses.
I would say that the lunch buffet was slightly limited (for green salads) compared to RCI, however, the dessert area was significantly better. We found a nice clean area to eat (no trouble finding a spot) and had a nice lunch with our friends we just met. Staff came around and offered Drink of the Day (which I had to have).
Located in the AFT section of the ship. Quiet, nice and clean. For some reason I swear that around 6:00 p.m. every night I'd get a smell of charred burger (like flame broiled burger king). It was just weird. It was a quick walk to the stairs, and as long as you could remember which MDR you were supposed to be at, it may be an even quicker walk to the MDR. Bathroom was nice and clean. Only 2 of the closets had a rod/hangers. So if you're going to fit 3 people in there, not everyone will have their own "closet" if you need hanging stuff.
Unfortunately traffic is very bad, so if you have an extra 2-3 days then I'd suggest doing San Juan. One day wasn't quite enough. Took almost an hour for the trolley to make it a short way, but it was also quite hot/warm, so walking would've been a bit much. We did do the Fort where the kite flying was at. Would definitely like to see more.