"IF" you do plan to visit Santiago, then Kokara Makara (spelling?) is a nice restaurant to visit. It is located right across the street from the momument.
I went there with my friend and his wife. Six drinks--four Pina Coladas, two beers--an appetizer, and three meals came out to around 2,000 pesos.
Camp David is also a nice restaurant to visit. But make sure you wear a long sleeve shirt and bring a light jacket because it might be cool.
The Plaza International is a nice and clean mall. The second floor has a nice food court with a variety of food and American Airlines is also located on the second floor.