According to the Vienna Convention on Diplomatic Relations that sets out the rules for diplomatic immunity Bush would not have diplomatic immunity if he left the country for any reason other than a diplomatic mission. It also states that he can be tried in international courts for crimes he committed while in office.
Some of you need to read more and pretend to know less.
http://untreaty.un.org/ilc/texts/ins...s/9_1_1961.pdf