People from other places come to south India for their own whys and wherefores. Thus their native language or known language differs, isn’t it? The common language that you can notice to teach Tamil or even any other languages is English. Well some can find it uneasy because of being belonging to different situations. Only if you are sure that you are comfortable and thorough with English you can proceed to learn by that way or else it will complicate both the learner and the teacher.