Basically, click MENU until you are back on the main menu. (You will know you are there because the Menu will stop changing when you click it because you've reached the top.)
Here's where it get tricky..Scroll all the way to the bottom, and then back up so the third item from the bottom is highlighted. Click that item.
Scroll all the way to the bottom of that menu, and then back up so the third item from the bottom is highlighted, and then click that item.
If everything worked right, you should see English somewhere on that list.
Unfortunately, I have, played around with the setting options on my Nano, so I may not have the order of the menu items in the same place as the default menu, so if that doesn't work, you will probably need to call the Apple Help Desk, and they'll be able to walk you through this same process. (You won't be the first person who has done this...I wasn't!)