Recently I posted about Deleting Project and the Project site from Project Center.
Now there is a new feature available (thanks, Microsoft), you can choose the Default Site Language, that means, you can create your Project Online environment in English and set the Default Site Language to be provisioned in Portuguese (Brazil) for example.
To do that access your Project Online environment, go to Server Settings under Workflow and Project Details Pages, click on Enterprise Project Types and find the option Site Language.
There are many languages available.
After you create the new Project Site, access the Project Site, go to Site Settings and under Site Administration click on Language Settings and remove the alternate language and save.
And done, now the Project Site will appear in Portuguese and you can save as a Template.