Yes. Its fine to have both versions installed on your computer. A CS6 version can co-exist with a CC version without causing any trouble. Sometimes, you need both versions to be able to work with multiple clients and deliverables.
Your Creative Cloud membership also includes access to CS6 apps. So if you ever need the CS6 version, head over to http://creative.adobe.com/, sign in, and download a CS6 app. For instructions on how to install CS6 apps see: Install CS6 app with Creative Cloud.