Hi nightrider1981,
Will the cloud Lync users and the on-premises Lync users use the same domain name? If so, you will need to deploy Lync hybrid. In this situation, the DNS records such as SRV records need to be pointed to Lync on-premises. For detailed information, you can refer to the following article:
Overview of Hybrid Deployments
http://technet.microsoft.com/en-us/library/jj205386.aspx
If the cloud Lync users and the on-premises Lync users will use different domain names, the required DNS records for the cloud domain need to be pointed to Office 365.
Thanks,
Mindy Pan