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

We are visiting Buenos Aires with Star Princess on February. We will check into the ship at around noon. The ship is docked overnight and will sail off the next day at 6pm. So we will have half a day the first day, and the whole day until about 5 the next to explore the city. Could anyone please recommend a private tour vendor they have used in the past? It could be a shared tour, it does not have to be a private tour for the two of us. We also wonder if the hop on and off bus has a stop within walking distance from the cruise terminal? Any information about Buenos Aires is welcome, what districts should we visit...etc. Thank you in advance.

I set up a ToursbyLocals all day tour for 11 of us for a December sailing. You might check out their tours and see if others want to join you.

We (group of 4) took a full day walking (which also included the bus and a taxi) tour with BuenosTours. It was fantastic. Our guide, Jessica, was an American expat who clearly loves BA and was so knowledgeable and informative. https://www.buenostours.com/buenos-aires-tours

The HOHO bus is not really walkable from the cruise terminal. We took the free shuttle provided by H R Stern at the port which drops you off at their jewelry store. You can walk to one of the HOHO bus stops in about five minutes at Galeria Pacifica. Stop number 12.

https://www.buenosairesbus.com/index.php

I bought tickets online on this site. Print out the ticket and take it with you. I found people very helpful in pointing out where exactly to wait by showing them the ticket.

Buenos Tours gets good comments. Check Trip Advisor and the Buenos Tours web site. Half day and full day tours.

Thanks everyone for the suggestions, very helpful for my ongoing research!