GUATEMALA CITY -- John Wilson holds a PhD in physics and has worked in the aerospace industry for over thirty years. Today he is selling cheese-stuffed pupusas -- a native Guatemalan delicacy -- from the back of a burro-driven wagon. , GUATEMALA CITY -- John Wilson holds a PhD in physics and has worked in the aerospace industry for over thirty years. Today he is selling cheese-stuffed pupusas... moreGUATEMALA CITY -- John Wilson holds a PhD in physics and has worked in the aerospace industry for over thirty years. Today he is selling cheese-stuffed pupusas -- a native Guatemalan delicacy -- from the back of a burro-driven wagon. , GUATEMALA CITY -- John Wilson holds a PhD in physics and has worked in the aerospace industry for over thirty years. Today he is selling cheese-stuffed pupusas -- a native Guatemalan delicacy -- from the back of a burro-driven wagon. view page