I just upgraded my MacMini Server from Lion Server to Mountain Lion using OS X Server. I am having the same problem with PostgreSQL that I did last year when I first instal
i make in word by doing this:
dpkg-reconfigure locales
and choose your preferred locales
pg_createcluster 9.5 main --start
(9.5 is my version of postgresql)
/etc/init.d/postgresql start
and then it word!
sudo su - postgres psql