The horror, one must think. In many restaurants, you'd be lucky to get a marginal salad, some fries (no doubt cooked in only the finest of organic vegetarian oils ) and a piece of provoleta, cooked on the grill with the sausages and steaks. A couple days ago, I went to http://www.naturalezasabia.com.ar/home.html . It was decent. The vegetarian in the party of 2 really liked it, and I thought it was good enough to go back. Casual, but nice, fair prices, and if you spend any time here, eventually you will be craving vegetables other than fried ones called potatoes. It is in San Telmo, a few blocks from Plaza Dorrego.