This inquiry explores the relationship between intra-sentential codeswitching limitations after subject pronouns, negative elements, interrogatives and language-specific syntactic structures. Data are proposed from two languages with non-cognate lexicons that share identical phrase structure and syntactic mechanisms and exactly the same grammatical morphemes except for pronouns, negators, and interrogative words. The languages are the Quichua of Imbabura province, Ecuador and Ecuadorian Media Lengua (ML), consisting of Quichua morphosyntax with Spanish-derived lexical roots. Bilingual participants performed un-timed admissibility evaluation and language-identification tasks and simultaneous memory-loaded repetition on expressions in Quichua, ML, and diverse mixtures of Quichua and ML. The admissibility and classification data display a major effect for category of single-word switches (significant differences for lexical vs. interrogative, negative, and for admissibility, pronoun) and repetition data display significant differences between lexical vs. interrogatives and negators. Third-person pronouns (which need an explicit antecedent) also diverge significantly from lexical items. Logical-semantic factors may contribute to code-switching limitations.