Portuguese here. This is anecdotal evidence but, as far as I can tell, a lot of our proficiency comes, essentially, to constant exposure to the English language since the early to mid-90s. We don’t dub English-speaking media (apart from movies and tv shows more aimed at kids, but even then, Cartoon Network didn’t even have subs when I was a kid and I still watched it religiously), the video games we played when we were kids also didn’t have a Portuguese language option so we were basically forced to learn English.

And now that the Internet has become widespread throughout the country, the younger generation consume a lot of English-speaking content, so they have little trouble with speaking and writing in it.

This results in a good % of the population having decent to good English, not just the kids but a lot of people in their 30s (and some in their 40s) too.