Father de la Cuesta was a forceful, imaginative educated man. One of his unusual habits was that he liked to name newborn babies with names from ancient history. Alfred Robinson, an American hide dealer who visited San Juan, reported that he found "infant Platos, Ciceros and Alexanders."
Father de la Cuesta knew more than a dozen Indian languages. "The best way," he wrote, "to see and hear a new dialect is to associate mostly with old ladies and some young ones for you must see it as well as hear it, as in talking it is necessary to mouth your speech, working the teeth just as you would when eating, and," he adds, "after half an hour's talking I get hungry." Again he wrote that "a verb with no past tense is above my comprehension but I will ask God's help and will learn, though it take bloody tears." While at San Juan Bautista, he wrote two important works: a compendium of Indian phrases, and an exhaustive study of the Mutsumi language which received scientific recognition in 1860.
After Father de la Cuesta left San Juan Bautista in 1833 when the missions were secularized, he joined the Franciscans at San Miguel where he remained until his death in 1840.