No. There's no reason to assume they don't speak English. I'm sick of the number of immigrants who pretend to not understand English and demand an interpreter. It gives a lot less credibility to those who say they really can't.
It said they were Iraqi Americans. Thee men were supposed to be training Marines in Camp Pendelton.
If she were overseas, the yes, she should have expected to hear another language. This was San Diego to Chicago.
Also, English is almost universally spoken overseas. The same cannot be said of arabic. And if English speaking people were know for flying planes into buildings then people would have a right to be suspicious of them also.
People overseas assume that I do not speak their native languages when I travel. You should visit Miami...most people speak their native language when in a group because usually, not everyone speaks at the same level. Not everyone is talking about you behind your back.