There are a couple of ways to do this:
1. Create a WCCP access list using CM GUI or CLI
http://www.cisco.com/en/US/docs/app_ntwk_services/waas/waas/v411/configuration/guide/ipacl.html
2. Create a new application and classifier for the IP subnets you do not want optimized and apply a no optimization policy.
3. If inline - you can remove vlan to be optimized. No VLAN ALL, then ad vlans you would like to optimize
