INSTALL does list locales as prereq

The INSTALL documentation should have locales-xx
mentionned as a prerequisite if you want to use a
language other than English or the default language
available on the server.

Suggested text

"b. locales for languages of the surveys

Gettext requires that the locales-xx package be
installed for each language that you want to use.
You need to be sure that locales are installed for each
language.

Under Linux you can list the locales already installed
useing the command.
locales -a

If you do not have Gettext and the appropriate locales
installed, all surveys will be in English.
"

from rwheeler@artifact-software.com