On the eve of the Arab Conquests, the Levant was largely Christian. These Christians of course were also deeply divided and belonged to various theological camps: broadly speaking Syria can be said to be mostly miaphysite, whereas Palestine was largely Chalcedonian. Aside from the Jews, there were also the Samaritans. Presumably there was a pagan minority as well, but we have little to no evidence of them. As the Levant was still part of the Roman Empire at this point, these people would have used Greek for their dealings with the bureaucracy (if they were part of the elite), Greek or Syriac for their literature (if they were literate), and their local dialect for their daily life (generally some form of Aramaic). There were also many Arabs living on the fringes of the provinces and some even had estates within the empire; some were Christian (mostly miaphysite), but others were pagans. I'm afraid I don't know anything about Levantine demography after the end of late antiquity - you might have to post a new question to get other experts' attention!