Console versions of MW3 are tricky because they don't have "language packs" in the same way PC does. However, the if you change your system settings.
If you own MW3 on Steam or Battle.net:
You do not need to risk your computer's security by hunting for sketchy file downloads. For the vast majority of players, the is already waiting for you inside your Steam settings or your console's language menu. Call Of Duty Modern Warfare 3 English Language Pack Free