The answer depends on whether you are in a building managed by Medical Center or Campus.  See "How do I determine whether my building is managed by Health or Campus?"

If you are located in a Campus building:

See the Campus Signage page on Campusplanning.ucsf.edu.  You can submit a request directly via Campus Life Services. 

If you are requesting signage for a Medical Center building:

Submit a request through Medial Center Service Now.