1. Barboca de Cordero
This hearty snack, which translates as 'lamb barbeque', is a favourite of mine when in Xochimilco, Mexico City. Here you punt along the city's "floating gardens" - all that remains of the lake that the city was originally built on in its Aztec heyday - in a colourful boat, being serenaded by mariachis and stopping the occasional vendor for a drink or a bite to eat. On a Sunday it's also the setting for a huge jumble of stalls selling lamb sliced straight of the spit. Seriously tasty.
For a quick and simple lunch, try blue corn tortillas filled with nopal, a type of cactus. Vendors use the leaves of the prickly pear cactus, de-spike and skin them then slice them up; they’re delicious and taste a bit like avocados - but are more interesting to tell your friends about.
The last time I was in Mexico City I found a great stall just in front of the National Palace in the main square. There was an old indigenous lady sitting on a stall surrounded by three snotty-nosed children, selling this tasty dish to a queue of hungry chilangos (residents of Mexico City).
Cuisine from the southern state of Oaxaca is truly some of Mexico's finest, but my favourite treat while in Oaxaca has to be the tlayuda - a crispy, dinner-plate-sized tortilla coated with refried beans, cabbage, avocado, meat and Oaxacan cheese. The dinner-plate comparison is no coincidence - the tortilla basically forms the dish for all the delicious toppings that are piled on top. My favourite type is the tlayuda cecina, which includes chilli-crusted pork cooked directly over coals alongside the tortilla. This street snack is so delicious you may struggle to make it into Oaxaca's formal restaurants during your stay.
Tacos are a staple of Mexican life. Perhaps my favourite kind is the classic taco al pastor, which offers a distinctively Latin variation on the traditional kebab, topped with coriander, lime juice and hot salsa. The showmanship of the vendors often comes out in the way many of them cut the pork from the spit and catch it from a great height in the tortilla!
If you're by the coast make sure you also try seafood or fish tacos, which are every bit as delicious as their meatier counterparts. Some of the best I've ever had came from a garage forecourt full of lorry drivers, so don't discount stalls based on an unglamorous location - the food can be amongst the best. If there are a lot of locals eating there, it's always a good sign.
Tortas, the Mexican equivalent of a sandwich, are available all across Mexico in pretty much any form that you can imagine - I recommend the sincronizada version, layering up cheese, ham, salad and tortillas.
For a bigger lunch, complement with a bag of fresh mango or watermelon from a fruit stall. Try it at least once with the chilli and lime accompaniments, which balance with the sweetness of the fruit surprisingly well.