Callejón del Diamante is an alley near the cathedral, with a half-dozen inexpensive restaurants that cater to office workers and students. One, La Sopa, offers a daily blue-plate special for 50 pesos. The restaurant at the Mesón del Alférez hotel serves traditional Mexican food and some regional dishes. At night you can get some delicious tamales at Tamales y Atoles Doña Adelina (tel. 228/841-0317) at Ursula Galván 108 (3 blocks west of the Parque Juárez). Each tamal goes for 14 to 20 pesos, and they are big enough that two would make a meal.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.