I don't have much regarding Alarcon and Rivera, but I hope you find this interesting. In 1567 five 5 spaniards from Extremadura, Espana shipwrecked off the coasts of Sinaloa founded Aguacaliente de Garate; amongst them were marquez Don Juan Jose Garate, Don Jose Gabriel Valdez, Don Antonio Maria Lizarraga, Osuna and Tirado. my great-grandfather was Ignaciao Guerra Lizarraga b. 1862 married to Domitila Valdez Garate. My family tree going back many generations, I have found Garate and Lizarraga. Somewhere down the line I'm sure we're related. Hope you find this interesting.