The usual problem with this kind of person is that they really aren't teachable. Being willing to learn, willing to take advice, willing to adjust their plans and schedules based upon what they learn are all hallmarks of someone who can be helped.

When they are stubbornly determined to 'head out' in a couple weeks (or whatever all too brief time period) they really aren't teachable. You have no responsibility to teach them what you can before they go.

If they can't absorb the 'First' lesson - i.e. 'Don't go until you're prepared and you have a bit of local experience under your belt', then they won't learn many of the other lessons that must follow...