All language translations are stored on lang.moodle.org - not within the actual plugin download. Once you have installed the plugin you might need to update your language packs - click the 'Update all installed language packs' button in Settings > Site administration > Language > Language packs.
If that doesn't work it's likely that your language hasn't been translated for the attendance module yet - you could do this for the community by submitting this on http://lang.moodle.org/