Yes for the love of god don't teach em to read it first. A good tip I can give you is follow the total imersion policy. Discourage the speaking of their native language. Try to keep the whole class in English, when talking to each other, unless you are explaining something or teaching. That way it forces the students to give up that safety net of their native language. This way they will become more comfortable speaking it in class, and the threat of being embarrased about not knowing the words will insure they study.