Multisite Per Site Registration

Hi there,
I am running a wordpress mutlisite configuration.
My main domain is domain.com and I have also a spanish version (subsite) : domain.com/ES.
I would like that user can register subsites from both my main domain and the spanish subsite.
If you allow user to registry a site I have to redirect them to the wp-signup.php page. But this file is located in your main wordpress site. so first, this is a redirection and the user leave the site and second, the form is in the main site’s language. The signup URL for the main site is “domain.com/wp-signup.php”. What I would like to is allowing people to register a new site directly from the subsite in spanish for spanish people and from the main site for english people. So one register form will be in spanish and the other one in english. With an URL like this “domain.com/ES/wp-signup-spanish.php”.

I’m looking for something like this :
http://halfelf.org/2012/multisite-registration/

Making a custom signup template for each website

I follow the steps and everything is working great until I click on the signup button, which redirect me to a not found page. (http://halfelf.org/2012/multisite-registration/)

Basically I want when people want to register for a subsite I redirect them to the specific signup template (just making the same signup process as the main site) with activation.

Could you help me please?

Thank you .

Mark