The use of English-origin spontaneous loanwords (e.g., "la babysitter," "el counter," etc.) in otherwise Spanish discourse is criticized by many as a strategy that bilinguals use to compensate for a lack of lexical knowledge in Spanish. The purpose of the current research is to examine the question of lexical proficiency as a motivation for the use of these words in the Spanish of Las Cruces, New Mexico. The data for this study derive from translation tasks administered to 15 bilinguals who were asked to identify Spanish equivalents of spontaneous loanwords that they themselves produced during interviews. We analyze the impacts of lexical variables (the repetition of Spanish equivalents in discourse, lexical frequency of equivalents, and cognate status of equivalents) as well as experiential variables (participants' frequency of Spanish use, their parents' birthplace(s), and years of formal education in Spanish). Results show that bilinguals, particularly those who were raised in homes with at least one Mexican-born parent and those who use Spanish frequently in daily interactions, are very proficient with the Spanish lexicon and do not use English-origin spontaneous loanwords as a way to compensate for a lack of lexical knowledge in Spanish.