You name it, and it's available in Quito. Restaurants range from the basic places offering chicken and rice for $1.50 to international food with very expensive prices. The country benefits from all worlds, with a variety of dishes inspired by both coastal and Andean produce. Seafood and fish is fresh and delicious, while meats, particularly pork, are excellent. These combine with typical ingredients such as potatoes, plantains and all sorts of tropical and Andean fruits.
A good area to head to for eating out is the Plaza El Quinde (or Foch) which is in the Mariscal district at Foch y Reina Victoria. There are dozens of restaurants and eateries all around this area. La Floresta, up the hill from the Mariscal around 12 de Octubre, also has many fine restaurants. The La Floresta traffic circle turns into an evening market after 5 pm and the most popular dish served is tripa mishqui (grilled beef or pork intestines).
Churrasco is a a great Ecuadorian version of a Brazilian dish. Tallarin is a popular noodle dish mixed with chicken or beef. Chinese restaurants are known as "Chifas" and are very abundant. Chaulafan is the local term for fried-rice, a very popular dish. Cebiche (also spelled ceviche) is a very popular dish in which clams or shrimp are marinated in a broth. Worth trying, but look for a well known restaurant with many locals to be sure you are getting fresh seafood.
When buying from lower-priced restaurants or shops, if you only have bills larger than a $5, it's a good idea to get them changed at a bank first.