I would say that a person that eats very basic things and is careful with money can eat at home for about 20 pesos per day. This would be 3 meals and maybe a merienda as well. These would be using supermarket products, with limited amounts of dairy and meat. If you include meat, fiambres, or prepared foods, you are probably looking at around 40 pesos per day, per person. If you are talking about eating meals out, a very basic lunch out is about 50 pesos and basic dinner 75 pesos without alcoholic drinks of course.
Yesterday I bought, 1 container of "queso blanco", 250 gr calabaza, 250gr potatoes, 250gr carrots, 2 pkgs of spinach and 1 head of garlic. At the carnicería I bought 1kg of cuadril. Total 63 pesos. This was enough for sunday night and tonight's dinner for both of us. Comes to $15,75 per meal and that is not counting the oil, salt, spices used for cooking and the iced tea (unsweetened, made from tea bags) that we drank. So truly about $20 pesos per person per meal. Not even close to the $6 pesos per day that the government is talking about.