Today I changed the language settings of my Team Web Access account for Team Foundation Server 2013 and here is how to do it for the ones looking for this info.

1- Open Team Web Access

2- Click your Name on the top-right corner

3- Click “My profile”

4- Click “LOCALE” tab on the window that opens

5- Change the “Language” under “SETTINGS”

6- Click “Save changes”

Hope this helps.

Good Luck,

Serdar