Arrived in BA today. Called uber from ezeiza and paid with card no problem, got the mep rate with visa.
I was looking for a banco galicia atm just for a quick cash run waiting for monday. I tried 3 banco galicias around palermo and no cash on any of them, only the one next to alto palermo shopping had cash but it only let me withdraw 20000 instead of the reported 40k max.
Charges 3600 comission and gives close to mep rate, I got 730 per dollar unfortunately all in 500 bills.
I was able to exchange a 100 usd bill in "cambio berlin" near alto palermo shopping as well. (for 740 rate since it was a sunday and cuevas "protect" themselves on weekends and give you a worse rate).
Seems like the best option is to always pay with card, too bad there are no atms that can dispense a high amount of high denomination bills. If there was an atm with a 80-100k limit close to the mep rate like banco galicia it would be perfect.