Plotalot comes with several language translations contributed by users. Look in the component language directory to see the language files that are installed:
<site>/administrator/components/com_plotalot/languageJoomla has a language debugging system which is very easy to use. Go to Global Configuration, System, and enable both debug settings. Then, at the bottom of every page of your site, you will see a lot of information about which language files are loaded, and details of any errors.
If you create or update language files, please send them to us so that we can include them in the next release of Plotalot.