There is little effort required for finding local food around Monterrey. Driving through the canyon or the city, you will pass by numerous restaurants and street stands serving a number of traditional foods. The local favourite is Elote which is corn kernels covered with Mexican spices, mayonnaise and creme. They are delicious, cheap and filling but you may want to limit yourself to the number you consume. One bag of Tostadas with elote and all the toppings racks up to about 1200 calories!
As with most things in Mexico, local knowledge trumps all. If you’re looking for the greatest dishes around, you should speak to the people who run your accommodation to find out where those hidden gems are as it’s unlikely they have a website.