To enjoy the best experience and full audio/video modality when joining a Lync 2013 on-line meeting from a Mac* machine and supported platforms, the best option may be Microsoft Lync 2013 Web App. This does not rely on the presence of Silverlight and complements users already running Lync for Mac 2011 (available as part of Office for Mac 2011).
Simply download the LWAPlugInstaller.pkg web plug-in at the prompt when joining a Lync 2013 conference for the first time. Allow installation to complete - although only one option is available “to install for current user only” - and voilà, you can join the meeting using the built-in Safari or any installed Internet browser e.g. Mozilla Firefox. You can even change to your preferred language on-the-fly at the top right hand corner.