Buenos Aires in January

I enjoyed BsAs immensely but was there in their late spring. I loved the pedestrian streets Calle Florida and Calle Lavalle and stayed right smack at their intersection at the Hotel Gran King Hotel - modest, but wonderfully situated)
Every direction I walked on those streets took me to something wonderful and the streets themselves were full of people, shopping, cafes, restaurants, grill restaurants, gelato stores, shoes, leather, the elegant shopping mall Galleria, street theater, music, dancing (always a show right at the intersection of the two).
I did get ripped off by my Radio Cab driver in a fake currency swap when he kept insisting the bills I was giving him were all fake and I stupidly kept giving him more which he "returned" to me and told me they too were fake -- but in fact he was switching these bills and handing me back fake ones for the real ones I had given him. This was a "radio cab' which are supposed to be the safe ones so watch out and only use metal coins with them.
So being seniors do watch out for being targeted. Keep to streets where there are people about and this did happen when getting a cab in the evening from the very touristy Porto area near Las cabanas Lilas steak restaurant. But most of the time I just walked and walked in all the other far less touristy neighborhoods and it was fine, as was using the underground. Taking the train for the hour trip out to the delta islands was also fascinating both for the scenery along the way and again the theater of the people inside the train cars.
if there are any performances at the opera house I would try and get tickets but it might be out of season, but even a tour of the house will be well worth it. A lot of your enjoyment of BsAs will be eating - not a land for vegetarians so visit a restaurant website and see what recommendations you can find, including which tango show may be the better of the many offered.
And did I also mention there were gelato stores on almost every block and they have dozens of flavors beyond your imagination. Great dining city and easy on the pocket book too, at least when I was there. Though the great irony is whatever I saved went back into the economy after that little currency switch in the taxi cab that night - learn how to tell what is real by looking at the water marks, as silly as that may feel to do every time you get bills back. This fake currency racket is pretty pervasive there.

The falls are great but are not at all close to Buenos Aires. You are looking at a relatively expensive round trip air ticket, one day to fly there, one day to visit the falls and one day to return to BA.
We used the taxi driver who was recommended in ITN and he was fantastic. His name is Pablo Menendez and his e-mail is pablo3menendez@hotmail.com. He picked us up at the airport at 11:00 PM. We also had him transport us for a day tour the last day we were there so we could see sights that were difficult to easily get to on public transportation. He then dropped us off at the airport for our trip home. Excellent!

The falls are incredible.
We booked a package after we arrived in Bs.A.
Spent 2 nights there and loved it.