What I would suggest is download a Cracked version of Black ops from where ever, and then copying the files you need to the Steam directory.. Should work, I'm also in the same boat as you. My copy is Polish only, sadly I didn't know this before I activated it on Steam, so I have to do that.. I'm going to try it myself, but the way I'm thinking there shouldn't be any issue.. Let me know if it works or not.
Well I have checked this and it is confirmed working. All I did was copy the main folder, and the zone folder from one to the other. And verified the game cache once again. And before you know it, the game was in English! My only concern is that the Custom Classes, are named in Russian also, and that was the only one that didn't change to English.. Is there a certain file, I need to look for in order for it to be fixed? Thanks.
EDIT: Sorry for the double post, I'm not sure if I'm allowed to double post..