He knew Abydonian and English at the start, as well as some other languages his classicist parents would have taught him (including Latin). During the "Fifth Race" chapter, he worked pretty extensively with Jack, and Ancient became mostly his, as well, though I'm not claiming he's fluent (in other words, since my Daniel doesn't know as many other Earth languages as adult!Daniel would, he gets to concentrate even more on the alien languages that no one learns from an Earth-based education).

I've always wondered what happened to all of Machello's stuff. I wanted some explanation, at least.