Which address do you type in (in your browser) when you want to access your sites? I also run XAMPP on a Mac without internet connection and it is running fine. Your sites should be accessible via http://127.0.0.1/
. If that is not the case, maybe the sites are not right configured, for example when you had told Joomla! that the base-url for your site was http://192.168.1.2/
(or something similar).