Issue with Tales from the Borderland

Have you tried right clicking on the game and change the language on the properties?

maybe try to change steam's language to english, I know that Valve games try to use the steam client's language, maybe this one works the same way

http://forums.steampowered.com/forums/showthread.php?t=2732955
I know it's a different game, but who knows, it might work

right click the game on your steam library the game you want to change and choose proprieties in there you can change language of the game

I just did a search on TFTB's steam forum and it seems like the only solution is changing your system's language to english.
Try looking through TFTB's folder and if you find localization/language folders delete all of them except the english one. Then the game would have no choice but to use english for everything.