I wrote about this before hitanykey.webs.com/mar142012.html , but Facebook keeps changing things. So until they change it again, here's an update.
I just had a computer bought to me, a Windows 7 laptop, the owner said that the language on her computer had changed. She mentioned she was on Facebook when it happened. So I turned it on but everything seemed normal so I opened her browser and went into her Facebook account and it was changed to what I discovered was Portuguese. The hardest part is knowing where to click to fix things right.
I'm assuming here you can't read the language enough to get it set back.
If your using Chrome you probably will have no problem if Chrome gives you the option to translate it. Otherwise do the following.
Sign Into Your Account As Normal
Go Into Your Account Settings. That is the little upside down triangle and when the menu drops down the menu is divided up into five sections with gray lines. The settings option is in the fourth section, third item down.
Click on the Language symbol, blue ball, under the red ball with a white dash in it and above the world globe.
Then in the first line click on the Edit option, whatever language it is in.
Then you get an option to choose your language in the drop down menu.
Finally click on the blue button that in English says Save Changes. It should work immediately.
I had to fix this problem before for someone else. How this happens? I can only assume that this happens when you click on a link to download an app and it changes the system settings.