Generally, you can just do a port command by itself when you're doing something that reads - like "port list active". But you probably want /opt to be owned by your admin user, so any command that modifies it would need to be run with sudo. People don't always put sudo in front of every command when writing because it's like saying "Simon says" every time. And some people log in as the admin user, or set up ports with /opt owned by a non-admin user so sudo isn't required to modify it.
Also, instead of the long launchctl command, you can just do
sudo port load postgresql93-server
which does the same thing.