Not sure about the football - But Down Town Matias show the Rugby when Ireland are playing, so worth a shot. The one in Recoleta by the Buenos Aires Design place, was a good choice for us when the Grand Slam took place (If you know where the Hard Rock Cafe is, its close to that).
The most well known Irish Bar in town, The Kilkenny, doesn't do TV, so don't bother with that one. I haven't been to The Shamrock at 1220 Rodriguez Pena St, but its a possibility - But the best bet is to give Down Town Matias a call, or drop in and ask - That's how we found they would show the Rugby. Failing that, maybe The Alamo would be showing it - If you can get past the Baseball and Hockey (or whatever other US Sport is on Saturday).
In an ironic way, I'll be in Mayo at a conference this weekend, watching the Ireland match on TV, and following that, we have LIVE coverage of the Argentina v Peru game -
Failing all the above - I know a web site that streams most soccer matches and pretty sure it will show our game. PM me if you need it.