Ask him. If he says 'no' then give him 2 weeks notice and start looking for a boss that's cool with that. (That's how you negotiate. If are not ready or willing to leave the job, then you are merely arguing with him.)
This may be the path I end up taking... "I will be taking 2 months to go out of the country. I'd like to be able to work remotely during that time, or we can start making arrangements for someone to take over my responsibilities"?
I'd be precise about the plans - "May and June 2012" and so on.
Actually, many people quit jobs just so that they can take an extended vacation.