Actually, the portrayal was pretty believable for a 10-year old Filipino who doesn't have to speak English outside of school. Most kids in the Philippines are taught English from age 7 onwards. The quality of teaching varies a lot, and even adult Filipinos may be reluctant to speak English with foreigners, but most people there can at least understand English.
shareEnglish is the 2nd of the two official languages in the country, it's taught starting in Nursery school actually and not Grade 7 alongside Tagalog, the 1st official language.
It was also an unincorporated territory of the United States for almost 50 years until gaining independence and had a huge influence on the country culturally and linguistically.
So yeah, believable.
--------------------------------
-Pearls before swine-
[deleted]
Even in small towns where few foreigners go, most people know a little English. I was surprised at this when I visited some small towns on Mindoro Island, where at least in the 90s there wasn't anything really in the way of foreign tourism (I've heard that's changed some since though). Did that in the US Navy to get out of Manila the second time our ship pulled in there.
As someone else said, they are taught it in school.
Also, Salvador didn't seem to know a whole lot, when he was talking to that stranger who ended up abducting him. About as much as you'd expect someone to who only uses it in one class at school, as someone else also said here.
Understanding is a three-edged sword.