So, Inkscape-0.46-3-TIGER-UNIVERSAL.dmg on my 10.4 machine obeys the language settings from the OS X System Preferences. Not sure why this won't work for you.
Jon, could you please run the following command (used by Inkscape on OS X to set the LANG variable) and report the results for the languages you are trying:
export LANG="`grep \"\`defaults read .GlobalPreferences AppleCollationOrder \
2>&1\`_\" /usr/share/locale/locale.alias | tail -n1 | sed 's/\./ /' | \
awk '{print $2}'`.UTF-8"
echo $LANG
If you have your language set to spanish you should get LANG="es_ES.UTF-8", or LANG="fr_FR.UTF-8" for french, etc.
Could you also show the results of just running "defaults read .GlobalPreferences AppleCollationOrder"
Thanks,
Michael