Budget

There are a lot of al paso (walk through) places to eat; you eat standing up or in high chairs at the bar. Meals vary from hot-dogs (panchos), beef sausages (chorizos, or its sandwich version choripán), pizzas, milanesas (breaded fried cutlets), etc. Don't forget to indulge in the perennially popular mashed squash - it is delicious and often comes with rice and makes a full meal in itself. It is perfect for vegetarians and vegans to fill up on.

Mid-range

You can go to a huge variety of small restaurants, with cheap and generous servings, most notably the ones owned by Spanish and Italian immigrants. There are also many places which offer foreign meals, mostly Japanese, Chinese, Thai, Arabic, Spanish, and Italian.

Siga la Vaca. , several locations throughout the city, notably in Puerto Madero and Costanera, offers buffet-style asado fresh off the grill and includes a well-stocked salad bar. Including wine, approximately $10 per person. 

Las Cholas, Arce 306, ? +54 4899-0094. Great parrilla specializing in Northern Argentine found in Las Cañitas. The rooftop seating upstairs is a great environment. Don't expect to see many tourists here, just a lot of Porteños out for a three hour weekend meal. Try the Humita (made with mashed corn, cheese and spices) and Tamales (a sort of flour with minced beef) or anything off of the parrilla is great. Do not skip dessert.

Guerrin (pizza), Corrientes 1368, ? +54 4371-8141. Go for a great pizza in a really noisy environment 

El Farol, Estado de Israel 4488 (y Rocamora), ? +54 4866-3233. "Typical argentinian food": spanish + italian + meat. Very high quality. 

La Biela, (near the Recoleta cemetery). Very nice cafe just outside of the cemetery, shaded by an enormous rubber tree. In very ancient times, it was a saying: If you are not greeted at La Biela, you do not exist. When the bill comes, remember that the largest part of the cost was not the meal, but the right to show yourself there.

Splurge

The most expensive and luxurious restaurants are found in the Puerto Madero zone, near downtown, heading to the River Plate. But the nicer places in terms of decoration, food and personality are in Buenos_Aires/Palermo.

The Grill at the Marriott Plaza Hotel. Acknowledged as a five star restaurant it offers the finest international cuisine and is considered among the best restaurants in Buenos Aires.

Primafila Av. Puyerredon 2501, Tel. +54 4804-0055. Classy Italian restaurant where you will find thin crust pizzas due to their brick-oven (dinner only, not available during lunch hours). Extensive menu including salads, pasta, pizza, meats and seafood. Expect to pay around 20 dollars for a pizza.

Cabaña Las Lilas Alicia Moreau de Justo 516, Tel. +54 4313-1336. This place had the reputation of being the best place to eat steak in Buenos Aires. The steaks are enormous and succulent. Be warned if you eat here, count on them having to roll you out as you will be near explosion (prob best to wear trousers with elasticated waists!). Its a constant struggle not to stuff yourself with the mouth watering appetizers before your steak even arrives. When it does, you may chuckle at the little plastic cow figurine jabbed into the meat, smiling at you and bearing the words "Estoy jugoso," - "I am juicy" (meaning rare). Count on spending around 85 pesos for a steak, 12 for a beer, and 80 for a bottle of wine from their extensive list of Argentine and international vintages.

Restaurantino & Cafetino Olga Cossetini 791, Puerto Madero East; Tel. +54 515-0707. In this up scale Italian restaurant expect to find cloth napkins, fine silverware and snooty waiters in starched uniforms and long aprons. As alluring as these characteristics sound the real highlight is the food which is rich and decadent. Wide selection of main courses including fresh pasta in homemade sauces ($15-30AR), traditional chicken dishes incuding Chicken Marsala ($20AR-$30AR), and a variety of meats including Argentine parilla style steaks ($35AR). The menu of seafood is worth considering with rareties such as fresh Yellow-fin Tuna steak in a pesto sauce ($30AR).