I served in Resistencia (northern border with Paraguay) and actually flew back to the US with elders from that mission. The difference in culture was pretty surprising. They talked about how hard it was to get lessons and said the average baptism number was 1-3 for the whole time.
The people in that area of Argentina are more like Germans or Spaniards than other Latin countries. It gets very cold and snowy but the geography is spectacular and the food will be great. If your son doesn’t like spicy food he will be in luck. Argentines barely put black pepper on their food.