Change Language in cPanel
From Lunarpages Web Hosting Wiki
Can I change the default language inside of cPanel?
Yes, you can. Login to your hosting account's cPanel, and then click on the icon labeled Change Language.
From there you can select the default language you wish to use. These languages are available:
Once you have selected the language you wish to use, hit the Change button and the default language should be changed for cPanel. If you need to change it again, please follow these same steps.