Is the sentence "我们要怎么去机场？" ambiguous?
I am a native Chinese speaker.  This sentence is not ambiguous to me at all.  Here the "怎么" clearly means "how" to me.

But if you switch "要" and "怎么"，then the sentence will be like:

我们怎么要去机场？

Here "怎么" means "why".  This sentence sounds to me like that you have a guest coming by train but your boss asks you to go to the airport to pick him up.

Hope this helps.