How can you check if "public user registration" is turned on or off on the front-end? I'm trying to make a rather bullet proof front-end template that can toggle a sign up link based on if public registration is enabled or not.

Is there a way I can query to see if the system currently has public registration turned on from the front-end?
You can write a plugin that has a Template Variable that exposes Craft's SystemSettingsService->getSettings() method like so:

public function isPublicRegistrationEnabled()
{
    return craft()-&gt;systemSettings-&gt;getSetting('users', 'allowPublicRegistration');
}


You'd call it from the template via:

{% if craft.myAwesomePlugin.isPublicRegistrationEnabled() %}
    Enabled!
{% endif %}