The purpose of this study was twofold. First, this study was conducted to compare English communicative competency achievement between two different models of instruction. Adult English language learners (AELLs) participated in either the communicative task-based (CTB) or in a more traditional (MT) language instructional approach. The goal of the study was to determine which instructional approach best supported communicative competency achievement of adult English language learners (AELLs) by comparing the difference in posttest mean scores for two different approaches. Analysis of covariance (ANCOVA) was conducted to compare participants' communicative competency achievement controlling for pretest and for socio-demographical variables as covariate (age, gender, educational level, native language and time studying English). Results of the ANCOVA F(1,212) = 0.976, p = 0.324 indicated that there is no statistically significance at (p > 0.05) alpha level between the experimental and control groups adjusted posttest communicative competency means scores. The study also sought to determine the predictive qualities of native language (Roman/non-Roman) on English listening and speaking self-efficacy after controlling for participants age, gender, educational level and time studying English. Results of Hierarchical multiple regression (HMR) for listening self-efficacy indicate age, educational level, and time studying English explained a proportion of the variance in Self-Efficacy. The measure of Native language (Roman/Non Roman) slightly increase the model's ability to predict listening self-efficacy indicating native language (Roman/non-Roman) is significant (ß = 0.100). The positive coefficient suggests that Roman language is a better predictor of listening self-efficacy. Results of the second HMR for speaking self-efficacy indicate native language (Roman/non-Roman) is not significant at 0.05 significant alpha level F(1, 330) = 5.108, p > 0.05). The findings from this study inform policymakers, administrators, and classroom teachers to orient their planning, and teaching practice when implement ESL programs for adult learners. Consideration should be taking regarding learners' native language. Challenges may be greater when the script of the second language learner is not Roman. Non-Roman scripts do not have exact correspondence between alphabet characters and the relevant sound in the English language. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]