I already speak English, what else is there?
Walid is the head (of some sort) of a Muslim-American advocacy group, and yet does not know even a smattering of Arabic? The Qur'an is in Arabic. He probably has to deal with people every day whose first language is Arabic and may not speak English very well. He should at least be able to say phrases like "Hello," "Where's the Gent's?" and "My hat is brown." But it really doesn't matter that he doesn't know Arabic, after all a random person at CTU does.