I have a 34 year old male friend with cerebral palsy, will chiropractic therapies be of any help?

Depends. Chiropractic treatment will not treat the cerebral palsy unfortunately. There might be some relief with some of the spasms/stiffness associated with the disease; but any only 'soft tissue' work should be conducted. There have been no studies onthe benefit of chiropractic manipulation so let the buyer beware.
Unlikely. Back pain in cerebral palsy is complex and requires specialized care. If a physical medicine and rehab doctor is in your area, a consult would be very helpful. Causes could include spasticity, scoliosis, gait abnormalities, and early onset degenerative joint disease of the spine.
Limited. Chiro therapy provides a deep massage which can be temporarily helpful. No cure is possible and the basic cerebral palsy will still be present. A reasonable pathway is to ask the advice of the neurologist taking care of your friend to address the discomfort.