Changez is an engaging raconteur, and he seems to me to be fairly reliable because he openly shares feelings. For example, he openly shares the feelings he experienced after the attacks on September 11, 2001, which he knows will be unpopular with his American listener. Though the speech of others—the American to whom Changez speaks, the waiter, etc.—is implied, it is never stated directly, adding to our feeling that Changez is very much in control of this situation. He seems to realize, early on, why this American is there, that he is carrying a firearm, that he seems like someone in the military, and so forth. He even refers to the night as one that has great significance: this is not a chance encounter. His comment that Pakistanis must not assume that all Americans are "assassins" also supports the conclusion that Changez knows who the American is and what he is there to do.
Changez even mentions his "soft skills" training at Underwood Samson, where he was taught to recognize another person's agenda and redirect it; his skillful monologues seem to do just that. They humanize him and confuse his audience which, perhaps, has already drawn certain conclusions about Changez that may be fundamentally incorrect. In the end, we can only know what Changez tells us, and that leaves us with some unanswered questions, though I believe he does answer, if obliquely, more than it seems.