Gonzalo,
Currently, there is no way to restrict users to using select Project Types. However, you may consider using Templates for creating new projects to reduce the change someone would select the wrong Project Type.
Since Project Type is a core attribute of a Template and cannot be changed, you could create a base project template for each Project Type, then set the enterprise role such that user can only create projects from a Template. Although they'll still be able to use any of the Templates you provide, makes it much easier to ensure users are selecting the correct Type when creating a new project.
Hope that's helpful!
-Erik