Thank you for your answer (Google rocks ;) ).
I want wiki users see English texts without be logged.
I tried with several browsers on two different computers, and I see
always Spanish texts.
If I tell my users to log in the wiki, they are to access a form where
they see "Tu nombre de usuario", "Tu contraseƱa", ... very confusing.
It says (gtrans) you have to be logged-in in order to
change your
preferences..