This study explores the mental lexicon of Polish learners of Spanish as a foreign language (L2) through a qualitative analysis of lexical availability. Based on prototype theory and semantic network models, it analyzes learners' responses to two thematic prompts--'The Human Body' and 'The City'--to explore lexical associations, prototypicality, and network structures. The qualitative analysis is based on the lexical production of six learners drawn at random from a larger corpus of lexical availability of B2-level students from three Polish cities. Results show a hierarchical organization around stable prototypical cores and more variable peripheral areas. Associations reflect semantic, formal, functional, and experiential links, activated by priming. The findings validate lexical availability as a tool for investigating the cognitive structure of the L2 lexicon and highlight its pedagogical value for vocabulary instruction grounded in semantic categories and associative networks. [For the complete volume, "Lexicon Exploration in English and Spanish Learners. Educational Linguistics. Volume 67," see ED676344.]