Austin, Tex.

AUSTIN can’t claim taco primacy. That category is too broad, encompassing too many variations in style.

When it comes to breakfast tacos, however, Austin trumps all other American cities.

Roberto Espinosa, proprietor of Tacodeli and the breakfast taco interpreter of the moment, espouses a slacker consumer theory of why Austin  a city thick with creative folk, techies, students and politicians  has embraced breakfast tacos.

“People wake up at all hours of the day,” Mr. Espinosa, a native of Mexico City, said as he served a taco, piled with scrambled eggs and drenched in a purée of russets and jalapeños that he calls Mexican mashed potatoes.

“Maybe the first meal of their day comes at 11 in the morning, and maybe it comes at 2 in the afternoon,” Mr. Espinosa said, as customers queued for migas tacos, bound with jack cheese. “They want a taco, and they want breakfast. And a breakfast taco gets you both.”