BA is great. The best way to get to your hotel is via a private cab. A large desk for cabs is front and center in the arrivals area once you clear customs.
Multiple Kempinski hotels in BA. The nicest is in the Recoleta district - named for the cemetry. Lot's of restaurants and shops. Upscale neighborhood. Also it is an easy walk to the art museum.
I have never sailed from BA, but I doubt the port is by anything too great. Even if you get on the ship, it is still easy to get around. Cabs were quite inexpensive on my visit 2 years ago.
Sunday street fair in Sant Elmo is very good. Palermo distict is nice. The old port beyond the Casa Roja is fun with some trendy restaurants and a pleasant stroll. Florida Street is the big central pedestrian shopping mall. You also need to go to a Tango show.
If you have a chance, I would go to Iguassu Falls. It is an awesome sight on the border with Brazil. This is a minimum 2 day trip. The delta is a fun as is a trip south to the beaches.