Well, if it's purely a language issue, Al-Lah means literally "the God," taken from the Zeus figure of the old Arabic pantheon, so you're really just identifying the Supreme divine force of your mind; and, since no two people can really have the same idea of God anyway, you're not really saying anything but what everybody else is. If it's a political-ized issue... who can say? In Texas, I'd probably avoid using any Arabic at all. Just just me being scared of angry americans, though.... Who knows what a strict Christian who grew up in an Arabic-speaking environment would say... I don't know if we have any here
Well, Allah just means "lord" or "God" and is not an actual name. It's basically the same way in our language. So it stands to reason that the Arab-speaking Christian would also say Allah. After all, they ARE the same god.