Several years ago traditional argentinian diet was meat and nothing else. Now the times are changing and you will find vegetarian options in big cities. Note, that using animal fat (usually cow) for cooking is still very common, so sometimes your bread is not vegetarian, even if it has no milk or eggs. Double check contents when buying food in supermarket. Also, in many supermarkets you can find soy or lentil cutlets. Prices are higher than in Chile, so you could prefer cook for yourself rather than going to restaurant. Anyway, in some cities you could check chinese restaurants, they are cheap and have a buffet style, so you can choose something vegan for yourself.