Sounds like there's very little difference between that Mexican and myself, so that scenario works perfectly for me. Unfortunately, there's a big difference between me and most people, in most scenarios. In this case I think these differences also include the Mexican fellow you mentioned.
Consider the pitch for the Free State, the one that targets "like-minded individuals". We (probably) agree that this element is crucial to make progress and getting things started on a small scale in one small locale. So logically, it would require even more like-minded people to change the entire country. I haven't seen or heard of any evidence that suggests open borders will result in more liberty and less politics & regulations - only the opposite. Again though, I'm looking for truth, not to just be "right" so if you have info, spill it.
And it's true, I have no idea which Mexican will vote which way. I also have no idea which teenager may or may not be having sex, so I go with the law of averages which is pretty accurate.