As I will be traveling solo, does anyone have a recommendation for a eatery where I can get some authentic Argentine beef/steak in a very casual setting? Even takeaway would be fine. I read about a famous deli in Puerto Madero where I'm staying, but I can't remember the name right now. TIA
Depending on what you mean by very casual there are a lot of possibilities that would work.
Most Parillas seem to be very tolerant of customers (especially tourists) in jeans and a polo shirt. One of the least formal ones that consistently gets good reviews is:
El Establo
Paraguay 489
Tel: 4311-1639
This is right off of Florida street and is easy to get to by the subway (or cab).
I'm pretty sure that I've seen folks in T-shirts in there. It has the ambiance of a New Jersey diner (minus the chrome) but has quality beef.
Other possibilities include La Brigida (my favorite: decorated like a soccer-centric sports bar, minus TVs but with white tablecloths and nicer service) and Parilla 1880 (you'll see lots of families). Both of these are in San Telmo.