No, most Muslims don't speak Arabic. Depending on which country they are from they speak their native language. So An American Muslim speaks in English whilst a Japanese Muslim speaks in Japanese. Only Muslims from Arabic countries speak Arabic. Do you know that there are more Arab speaking Christians than the entire population of England?
Though Muslims are encouraged and do aspire to learn the Arabic language in order to better understand the Quran and the word of God which is written in Arabic. Most read the translated versions....but we all know that reading a book in its original language can give the reader a better sense of the message in the book. In this context Gods message.