The best thing to do is a full factory wipe and reset, so you can set the language at the lowest level.
Have a look at the video here, though this is a different model the concept is the same.
Switch off the tablet, then hold down the volume UP button and Power button together for around 15 seconds or until you see the droid, at which point you can release them.
Then you selecting the option 3 from the bottom, and then the one which does not say no (has more text\writing).
Use the volume up and down buttons to navigate\highlight the options on the menu, and press the power button briefly to select the option highlighted.