There's a wait, but there's no line. At lunchtime in Mexico City, this sort of huddle is common at street-food stalls and at storefronts that open onto the street. (It's a familiar formation at Mexican carts in Queens, too.) When the walkway is narrow and there's room only for a line, then you'll see a line, but otherwise the waiting customers manage themselves, generally with quiet resolution. Impatience, if expressed aloud, would be bad form; maneuvering for a more advantageous position simply isn't done. Everyone is served in due course.
Ultimately: tacos de tripa and suadero (14 pesos each, about 70 cents at the time). "Tripa" translates readily, but "suadero" is more of a mystery: It has no specific analog on the U.S. and European butcher charts that I've consulted. Meaty but with little muscle grain, this Mexican cut of beef is trimmed from forward of the hindquarters but rearward of the flank. For now, I'll just call it suadero.
Taquería El Torito
Calle Isabel la Catolica 83 (Calle de Mesones-Calle Regina), Centro, Mexico City