No, its on a per blueprint basis, not per page. But you have to add all possible templates per blueprint.
Check out the solution I suggested in this post if you want to allow the same templates for all blueprints: The changeTemplate workflow
Edit: Do you mean being able too change the template after the page has been created? Sounds as if you mean you cannot create a new page with a template other then the default page. That is defined in the site.yml blueprint, which has a create: default option in the pages section. This option means that in this section, only pages with a default template can be created.