Supposing you are using root
to run WO, you can creat an YAML configuration file for WP-Cli.
In such case, the file will be /root/.wp-cli/config.yml
.
The contents of the file:
core download:
locale: pt_BR
It is importanto to observe the indentation (two spaces), YAML is kinda sensitive about these details.
EDIT: of course you may create this file for whatever user, it just must be ~/.wp-cli/config.yml
.