There should be reliable wifi at the airports to get a ride. (That said, what is the AEP situation? I've not arrived there in a few years, and just finding the arranged ride (not an app) was a quilombo).

Taxis, for the most part, are reliable and inexpensive. Best to hail the ones from Premium or another "radio" service - the cars are typically better and you're less likely to get the rare rogue taxi. I don't ever recall seeing a taxi that takes CCs, but I'm only there every few months, so maybe I've missed something

You need to obtain a SUBE card for public transit (Subte and Bus) and finding them can be challenging, although some SUBTE stations can occasionally have them.

Lots of wifi in lots of places, so you should probably install Cabify, as well as What's App, which is the most common communication means (both texts and calling). Traveling without reliable mobile service these days is asking for trouble. I know that is more information or advice than you want or asked for, but if you're out and about and need help, you may find yourself helpless. I would certainly ask my home mobile provider what the daily charge (or however it charges) for out of country use, and make sure it will work, because in an emergency, it really doesn't matter if it is $5 or $20 or $100 to get you out of a situation.