Get back on the metro (still 5 little pesos) and head over to Chapultepec Park, one of the largest city parks in the world, and a major injection of nature into sprawling Mexico City. Admission to the park is free, and worth a stroll. It's also home to the Museum of Anthropology -- an absolute must for any first visit to the DF. Here you will find archaeological and anthropological artifacts from all of Mexico's pre-Columbian indigenous cultures. And at MX$65 ($3) for admission, you can't go wrong.
Where to eat: Eating on a budget in Mexico City is beyond easy, but you won't be dining in the glamorous restaurants in trendy Polanco. Oh no, it's street food for you, my friend. But this is an infinitely better and more traditional experience. In DF you can find cuisine from across the entire country. It's a dizzying array of tacos, tamales, quesadillas, roasted corn, grasshoppers (legit), all hot and delicious, all on a strict budget. The city’s indigenous tacos de canasta, filled with potato, refried beans, and chicharron, are easy to find throughout the city. They cost about 30 cents. Even if you eat 10 of them you aren't close to maxing out your budget.