Hey Rodolfo!
Portuguese is definitely an available and supported language for JIRA and JIRA Service Desk. Please follow these instructions to set it as the default language for your instance.
Sadly this is an all or nothing endeavor, as currently there is not support for a multi-lingual instance. There is a feature request for that however, which can be found here. I suggest that you vote on and watch the issue for further development!
Good luck!
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.