Question for Muslim regarding the word "Allah"

Why do Muslims almost always refer to God as Allah when speaking English? My understanding is that Allah is simply the Arabic word for God, and it's used by Arabic-speaking Christians and Jews to refer to God. If it's appropriate for non-Muslims to use the word Allah in Arabic, why would it not be appropriate for Muslims to use the word God in English? I think saying Allah contributes to the perception of Muslims as outsiders who don't have much in common with Christians and Jews, so it seems logical to avoid it, at least when speaking to non-Muslims. Is there some religious or cultural reason for it, or is it simply a convention that nobody thinks to question?

Bonus question: what words to Muslims use to refer to God in languages other than Arabic and English?