ScarySolstice: This might be a really stupid suggestion, but since you didn't write in your post how long into the game you've played...
Manny, being hispanic, sometimes speaks random words and phrases in Spanish, so even in the English version of the game, the very first line (after the opening cutscene with Manny and Celso Flores) is "Que es esto?" If you continue playing after that, it should be in English.
If you have indeed played further and it's all in Spanish, please disregard this post. :)
oh my! do feel silly:) though in my defence i did try all the other languages and play the first line of dialogue and those were definitely in the language chosen so it seems that it's just the english version where manny reverts. i didn't play any further becasue i have this choppy sound in linux issue whcih even pulseaudio won't make go away, here's hoping the patch fixes it
