It depends upon the context. In the US, both "disabled" and "people with disabilities" are acceptable/common usage, but whevenever possible it's preferable to mention the person first. That is, it's more appropriate to say "person with cerebral palsy".
As a "person with cerebral palsy" I endorse this guideline. I certainly prefer to be ackowledged first as a person, then as one who happens to have experienced birth hypoxia with resultant hemiparesis, equinus etc. Without going to extremes of "political correctness", it is a matter of respecting the basic dignity of the person being addressed. My friends are free to call me "gimp", "cripple" "spaz", etc.