Abstract This study explores variable Spanish subject pronoun expression (e.g., yo veo ~ veo ) in Spanish-English speaking children in different regions of the United States (U.S.): Los Angeles (LA), California, and the Tri-Cities area of the state of Washington. We also compare the U.S. children to monolingual Spanish-speaking children in Mexico. Binary logistic regression analyses of 2,064 verb tokens produced by nine U.S. children and nine children in Mexico, ages 5;11 to 7 years old, show that the children are sensitive to linguistic factors that typically influence children’s Spanish subject pronoun expression in their respective communities. In addition, we find that the LA children’s subject pronoun expression is predicted by lexical frequency. A subsequent analysis of the LA children’s frequent verbs uncovers two phrases with high degrees of prefabrication, yo creo and yo no sé, which, we argue, obscure the LA children’s sensitivity to Reference, all while acting as central exemplars of a [1sg+cognitive verb] construction.