You must travel, but one would find be remiss in their streetfood duties if they didn’t make a trip to El Centro to visit Los Cocuyos. Practically every taco is worth ordering, but the lengua, in particular, will render the specialty nearly inedible anywhere else. If you arrive early enough, the mollejas are also not to be missed.
If you would like to venture into a part of the city that is the polar opposite of Polanco, to a hole-in-the-wall that serves loaded chilaquiles for $2.50, there is a small place in Coyocan that fits the bill:
If you go, check out Churrería La Parroquia, a less-traveled-to churro destination than the famous El Moro, but you know what they say about those less traveled roads.
The elaborate experience of El Cardenal this is not; though if you lean that way, might I recommend the eminently homey, yet less-visited Fonda Mayora run by Gerardo Vásquez Lugo, the chef behind the acclaimed Nicos.
In Polanco itself, it must be noted, a rather uncharacteristic space serving nothing but cochinita pibil in a variety of forms is well worth stopping in at if you desire a quick snack: El Turix.
Consider trying a burrito, of all things, in Juarez, make sure you have them fry the cheese on the outside at Burritos todo mecate:
https://www.yelp.com/biz/los-burros-a-todo-mecate-ciudad-de-méxico
You might also find Caldos Ánimo intriguing , though it will be another trip, the fusion of birria and ramen is perhaps worth the shlep.
Would the grasshopper quesadillas at Bosforo count as street food? Or perhaps the stewed rabbit at the unnamed restaurant next door run by the same people?