Almost everyone in the technical field is comfortable with using the English language for their daily tasks.
As you know, managing future version of VMware vSphere will only be possible with the Web Client.
If you have already used the old trick to change the language of the java vSphere client like this:
"C:\Program Files\VMware\Infrastructure\Virtual Infrastructure Client\Launcher\VpxClient.exe" -locale en_US
"C:\Program Files (x86)\VMware\Infrastructure\Virtual Infrastructure Client\Launcher\VpxClient.exe" -locale en_US
Here is the other trick to change the language on the vSphere Web Client.: