Thanks very much to you both!
I'll be staying in La Recoleta about 8 or 9 blocks from the theatre but my little hotel will not have a concierge--I'm just hoping for a front desk staffed round the clock.
Sounds like I was really jumping the gun expecting tickets to be on sale already. (Used to months in advance in these parts.) So, I'll go see about a ticket when I get to BsAs. I will try for the second performance but will have apparel that won't be too horribly embarrassing if only the first night is available. (Being female, even with only carry-on it's easier to pack to span dress conventions.)
I am so excited to finally get to visit Buenos Aires, a city that has long called to me in spite of the fact that I usually wander around looking at how people build fences and what shape their barns take. Must have been all those Borges short stories.