The roads downtown were laid out 1609-1610 by Pedro de Peralta and his surveyor[1], who followed the Roman grid plan designated for use by the New World settlements[2] albeit not to the same high standard, especially after the Pueblo Revolt[3]. In 1610 the area was not part of any Pueblo[4] and no previous burro-using settlement had been there.

[1] "He and his surveyor laid out the town, including the districts, house and garden plots and the Santa Fe Plaza for the government buildings. These included the governor's headquarters, government offices, a jail, arsenal and a chapel." - https://en.wikipedia.org/wiki/Pedro_de_Peralta

[2] "In 1513 the monarchs wrote out a set of guidelines that ordained the conduct of Spaniards in the New World as well as that of the Indians that they found there." https://en.wikipedia.org/wiki/Spanish_Colonial_architecture#...

[3] "These structures had been laid out around a street grid and series of plazas—a practice that had become a standard for new Spanish settlements in the Americas and Asia—yet their irregular rather than orthogonal alignment seemed disorderly to Domínguez [in 1776]. ... The employment of the grid in town layouts remained in use even when New Mexico became part of Mexico and the United States, only to be replaced by the cul-de-sac and other American suburban models of development since the 1950s." - https://sah-archipedia.org/essays/PF-01-ART004

[4] "The Tanoans and other Pueblo peoples settled along the Santa Fe River from the mid 11th to mid 12th centuries,[20] but had abandoned the site for at least 200 years by the time Spanish arrived in the early 17th century." - https://en.wikipedia.org/wiki/Santa_Fe,_New_Mexico