Leonora Mendoza, singer and composer, was born in San Luis Potosí, Mexico. Leonora learned to sing from her mother who, some sources say, taught music in Rosita, Coahuila. She married Francisco Mendoza, also a musician from San Luis Potosí. They had eight children, several of whom performed with the family's troupe. Later, with her assistance, her three daughters became popular singers among Mexican Texans.
Leonora Mendoza passed on the repertoire she learned from her mother to her own children and in 1927–28 organized the family into a musical and performing troupe called La Familia Mendoza. The group performed traditional Mexican songs; Mrs. Mendoza played guitar, and other family members played violin, mandolin, and percussion. The group originally worked in restaurants and barbershops in the Rio Grande valley for small wages and tips. They sometimes "passed the hat" for money.
Around 1928 an advertisement in La Prensa seeking musicians to record songs drew the troupe to San Antonio, where they recorded twenty pieces for the OKeh label. For the recording project they called themselves Cuarteto Carta Blanca. With this recording, the Mendozas became part of the "race" recordings produced by such major recording businesses as the Victor Talking Machine Company, which ventured to San Antonio in the 1920s to put the music of Spanish-speaking musicians on double-sided discs. After recording the songs, for which they received $140, Leonora Mendoza, who was in charge of the family's shows, and her family moved to Detroit, where they stayed two years, performing for Mexican Americans in the Midwest. The group later returned to Texas and eventually staged its revue in the Plaza de Zacate in San Antonio to entertain shoppers.
La Familia Mendoza once again recorded music in the 1930s, with Leonora often singing the lead vocal and playing guitar. Because of the growing success of her daughter, Lydia, the family undertook tours throughout the Southwest and Midwest. Leonora organized and directed the shows, which consisted of music, skits, and comedy routines. Although her husband was opposed to educating their daughters, she taught all her children rudimentary reading and writing. However, none of her daughters ever received formal schooling.
In the early 1930s she and Lydia recorded several duets. Among them were two songs attributed to Leonora Mendoza: "Vale Más que Te Alejes" ("It Is Better That You Stay Away from Me") and "Desdichada de Tí" ("Disgraced by You"). When World War II started, La Familia Mendoza's touring came to a standstill due to gasoline and tire rationing. In San Antonio under Leonora's direction, two of her daughters, Juanita and María, forged a successful career as a duet, and she accompanied them on guitar. She convinced Arturo Vásquez, the proprietor of Club Bohemia in San Antonio, to let them sing at his club. Later, she was able to set up a better arrangement at the Pullman Bar. Eventually their group, Las Hermanas Mendoza, also made records. The success of the women was great enough to help them purchase their first family home in San Antonio. After the war La Familia Mendoza's show, now expanded to include Lydia as a soloist and Juanita and María as Las Hermanas Mendoza, toured six months of the year throughout the Southwest for consecutive years from the late 1940s into the early 1950s. Leonora Mendoza's death in 1952 brought the group to an end.