This dissertation delves into second language acquisition, sociophonetic variation, and speech perception, investigating how prior linguistic experiences and exposure to regional variations in a second language influence the decoding of dialectal linguistic cues. It aims to enhance the understanding of words pronounced with different phones and their impact on spoken language comprehension. The study involves 108 English-speaking Spanish learners, categorized based on their exposure to Spanish regions with /s/ weakening and /s/ retention. This categorization reflects their level of language exposure and perception of regional variation, considering that around 50% of Spanish varieties exhibit /s/ weakening. The participants' exposure to /s/ weakening varies based on their backgrounds, previous exposure, study abroad experiences, and teacher origins. The study employs various experimental tasks, including a language proficiency test, a listening comprehension activity, an AX discrimination task, and a language background questionnaire. Data analysis involves logistic mixed-effects models and correlation analyses. Results show that participants exposed to conditions where /s/ changed from reduced to retained in isolated word pairs exhibited lower identification accuracy compared to consistent word pronunciations. An important finding is a significant interaction among participants with experience abroad in an /s/ weakening environment when contrasting /s/ weakening with full retention of the sibilant sound. The study also explores how learners' ability to categorize regional phonetic variants affects their listening comprehension. It reveals that accuracy in the AX discrimination task predicts their performance in listening comprehension, demonstrating that strong performance in the former translates to better comprehension. Additionally, the research examines the influence of participants' language attitudes on their task performance. In summary, this dissertation underscores the significant impact of exposure to regional language variations on individuals' identification accuracy and language processing skills, emphasizing the need to recognize linguistic diversity in language education and research.