Hi landitus,
I think that there is a problem in your case. Setting the default language to Spanish will create the homepage in Spanish, but ALL the other pages will be under /es folder.
I'll check if there is a way to add an option in the settings to have the default language without the language sub-folder.
Another thing that in any case you should consider, is to avoid duplicated contents. So if you add a language, prepare all the translations before to link them.