To change your default language:

• Click on Language upper in the upper right corner. 
• Choose your language preference. 
  
  

The default language controls which versions initially appear on the Translation / Commentaries menu. When Spanish is the default language, Spanish translations appear by default.

suggestion:

Changing the default language preference will return you to the default STEP page and for that reason it is a good idea to set the language preference before you start searching.