I needed to do some work on a WordPress site a little while ago and all the admins were French – and I cannot speak French other than the popular swear words – so had no idea what was going on in the /wp-admin/ so needed some way of enabling my newly created user account to be in english while letting everybody else use french as they had been up til that point.
This wasn’t something that wordpress did out of the box so I did some scavenging around and found a plugin called “Bogo” that did it really well.
You can get it here: http://wordpress.org/extend/plugins/bogo/
Once you have installed and activated the plugin you need to navigate to the user account you want to modify (wp-admin/profile.php) and select the dropdown next to “Locale” and change it to English.