localization on wordpress
For Wordpress, make sure you have the following structure of files:

plugins/civicrm/civicrm/l10n
plugins/civicrm/civicrm/l10n/fr_FR/LC_MESSAGES/civicrm.mo
plugins/civicrm/civicrm/sql/civicrm_data_fr_FR.sql
etc


Reference documentation:
http://wiki.civicrm.org/confluence/display/CRMDOC/Installing+CiviCRM+for+WordPress