I have my Core setup as a subnet of my main network. I'll then connect my laptop to the external network side and play music using SoftSqueeze. You have to remember to open the proper ports for Squeezebox to connect if you're not on the LMCE internal network side.
Also, for security reasons, I use an SSH tunnel to access SqueezeCenter when on the road (hopping into one of my non-LMCE boxes on the external side of my LMCE network). If you have your Core connected directly to the Internet then I'd recommend just tunneling directly into it and not opening up the ports on your firewall. My setup is a little more convoluted because I'm usually accessing files on my non-LMCE boxes, too.