I've provisioned an RDS instance using Postgresql 9.3.1 and my application requires en_US.UTF-8. When postgres was locally installed, I would have to create the cluster using "--locale=en_US.UTF-8".
Now with RDS, my understanding is I need to create a custom parameter group, however my questions are:
Unfortunately, the only other answers I have found are specifically for MySQL.
This is set with the client_encoding option in the parameter groups. This information is buried in an appendix of AWS's documentation.