This is essentially creating your own patch.
In the root directory of your Black Ops 2 installation, find a file named localization.txt . Open it with Notepad. Change the first line from russian to english . Save and close the file. Specifics for "Portable" Versions
If you are looking for a "Portable" version or a "Patch" for a pirated copy, you will likely encounter malware. Most "Russian to English patches" found on random file-sharing sites are actually viruses or outdated cracks.
TechFix Archives Target Game: Call of Duty: Black Ops 2 (2012) Issue: Russian language lock (text/voices) Solution: Portable EN Patch + Registry Fix