If it was me, I'd probably take a taxi to San Telmo, which is on the EZE-side of the city center, have some lunch, maybe take a quick ride up to Caminito (La Boca) for a little local color, and then head back to EZE - you are on the side of the city where you have the easiest highway access and least travel time to EZE. If you want an inexpensive pretty good piece of meat at a place where eating alone isn't an issue, I'd recommend El Desnivel on Defensa (in the heart of San Telmo).

ps - when are you on that flight? I'll be on it in a couple of months. PM me if you don't want to post it in public.