Buenos Aires Private Tour Recommendation? Hop on and off Bus? Thank you

We are sailing with the Star Princess in February. We will check into the ship in Buenos Aires, the ship is docked there overnight and will sail off the next day at 6pm. So we will have about 1.5 day to explore the city. Could anyone please recommend a private tour vendor they have used? It could be a shared tour, doesn't have to be just for the 2 of us. We also wonder about the Hop On and Off bus, is there a stop within walking distance to the cruise terminal? Please share any info of Buenos Aires, what districts are the most interesting, and any info on the Star Princess, how is the dancing? Thank you in advance.