Like I said in the OP, my guess is he would just eat at McDonalds or Burger King every day. If you live where westerners live, there are western restaurants. Within walking distance of my hotel there was an Argentinian Steakhouse, three Indian restaurants, an Irish Pub, a bunch of French restaurants (being a former French colony, French restaurants are all over the place), and a couple generic sports bars.
Two of the most popular and available Vietnamese foods, Pho (a fucking awesome soup noodle) and Banh Mi (baguette sandwiches) are not spicy at all.