Copy & Paste text can not be done whilst in a game. Thats the bad bit. The SC2 console does not allow text to be copied / highlighted even when pressing F11 to view the message log.
However, it can be done after game - but is quite long winded process initially.
First Install Java
Then download a program called SCELight
Then run program and locate game.
Then select message log
Then highlight text to be copied
Then press control and C
Then paste in to Google translate
My hopes of trolling Russian players mid game are dashed, but at least I get to see thier responses to "привет, мой брат, как ты сегодня?" in english afterwards - which is amusing.
PS - normally they call me a retard LOL - in russian of course (опятьхвост)