While looking for food, Han comes upon a wrecked Jeep and some scattered supplies, and finds them guarded by a large German Shepherd tied to a box. When the dog starts barking at him, Han says--in English--"Good dog", then notices a box that says "K Rations" and heads for it. It's not likely that a five- or six-year-old Korean boy on an isolated farm in the hills far from any town or village would know how to speak and read English.
When the American soldiers come upon Han and his German Shepherd, which he has named "Lobo", Han--played by young Hispanic actor Manuel Padilla--gets angry and shouts at the dog, "Kill, Lobo!" "Lobo" is Spanish for "wolf"; it's unlikely, to say the least, that a small boy living in an isolated farming area in early 1950s Korea would be able to speak three languages--Korean, English and Spanish.
Regarded as errors: The Korean boy Han speaks English, but this is explained by dialog revealing he had attended a nearby missionary school. Also, Han knows the dog's name is Lobo by reading dog's ID tag.
While trying to outdistance the North Korean patrol tracking them, the GIs find a wild pig in the hills, kill it and cook it over a campfire. In real life the smell of a pig roasting over an open fire would surely have been noticed by the enemy patrol and would have led them directly to where the GIs were.