Why are foreign language registrants redirected to home page after registration? When someone registers an account in English (default language) the registrant is redirected to the Login page with a message: "A welcome message with further instructions has been sent to your e-mail address."

So far, so good.

But when a registrant select a foreign language on the registration page (like es for Spanish,) he is redirected to his profile page after submitting his registration.

Anyone knows how to fix this bug so that it behaves like the English registration? Or a workaround?
I wonder if your issue could be related to the language specific homepage (frontpage).

The relative URL to display as the front page is specified within admin/config/system/site-information. Make sure you specify a value for it that is different for each of the site's languages. To do so, you have to make it a "multilingual" variable (it should say "This is a multilingual variable.") in the description of that variable on that page.

For more details about this, refer to my answer at How to make content translation available for front page?