How to change path of taxonomy facet search
There is a version for Drupal 6 here: Taxonomy menu with custom path for taxonomy terms

However, it uses hook_term_path, which in Drupal 7 has been replaced by hook_entity_info_alter.

Too see note of how to convert this from Drupal 6 to Drupal 7, see guidelines on Drupal.org about  Converting 6.x modules to 7.x