Hi Osmany,
As described by Jim during Unicode conversion, you shall be performing export of source database ( non-Unicode) and import into target database (unicode). During this export/import process, entire database gets reorged. So you can see savings in form of reduced used database space.
Additionally as you are on Oracle 11g, you may activate table compression ( Oracle 11g feature ) on target database so that any new piece of information stored is compressed. This configuration can be activated before you import the unicode database into target system.
Hope this helps.
Regards,
Deepak Kori