Photo I shot at Mexico City metropolitan area. The urban sprawl is so huge that it encompasses several states. Public transportation varies from place to place within the greater Mexico City area to be able to cover all districts and boroughs.
At public transportation key places where routes link it is common to see street vendors and eateries. You can find tortas (the equivalent of hamburgers made out of french bread) as low as 1 dollar*, or amaranth bars (the ones they sell you at posh nutritional store elsewhere in the world) as low as 50 US cents*.
In this case this gorgeous lady sells jicama, which is not only nutritional but low-fat. She sells them cut and already ready set to-go. In other places they make their form as lollipops, called jicaretas. But in general you can have them prepared with chilli powder, chilli sauce, lemon, etcetera. Long ago they carried them out in the open, but now most jicama and fruit vendors display them inside a glass-protected case.
When in doubt, whenever you are going to buying food or fruit, be sure to ask them how do they prepare it. It varies from place to place, and one can learn more about how to eat it.
* Prices are given according to current peso-US dollar conversion.
Jicama vendor at Mexico City. Copyright 2013 Miguel Omaña.