Sibelius created a Southern California Users Group on Yahoo, but it's really open to anyone because it's online.  They had a few meetings in North Hollywood but turnout wasn't the best so I think they are going to just keep it as an online group.  It's a great place to ask your Sibelius related questions and the response time is usually very fast.

http://groups.yahoo.com/group/scsug/

Good call Jesse. I just joined. Thanks!