We were told they eat meat, and they sure do! There are delicious steaks to be had everywhere, for about 8-12 euro. The best bet is just to order "bife de lomo" everywhere. Potatoes and suchlike often have to be ordered separately.
in Patagonia they have Patagonian lamb (I can especially recommend the one in the restaurant called Las Barricas). In Iguazu they have the traditional local fish (surubi, dorado and pacu). The only reason it became traditional is probably because they didn't have anywhere to put cows to pasture, or any better fish. Avoid if possible. They do also have salmon and steelhead trout, so the fish lovers are not totally fucked.
The have quite a lot of sushi places, I even saw a kosher sushi place in Buenos Aires. My one and only attempt at sushi revealed that the restaurant only had four kinds of fish: salmon, tuna, shrimp and an unidentified white-colored fish. They did a very good job out of it, much better than I could ever imagine anyone doing, but I decided to leave sushi at that.
Anything sweet either looks very suspicious or contains a lot of dulce de leche. I happen to like the stuff; if you don't, Argentinian pastry is probably not for you.
Finding the wine to our liking was a challenge at first; later we fould a producer we liked a lot, Luigi Bosca. Among local beers, El Bolson totally rules.
They make good coffee. Really good coffee, though in all my travels i still haven't found anyone who'd brew coffee as good as the guy near the big market in Istanbul.
There is a local specialty called cappuccino italiano. That's as opposed to the regular cappuccino, although occasionally you ask for regular and get italiano. It's cappuccino with cream (in addition to milk), cocoa and cinnamon, which makes for a surprisingly pleasant combination.
Ice cream in pretty good. Normally I like coffee, caramel and green tea flavors, but in Argentina they make very good ice cream flavored with strawberry, raspberry and other berries, often combined with mascarpone. I think their secret is that they put enough berries in there.