Where can I find statistics on people with disabilities?

The World Health Organization does not have any data on the numbers of people who have disabilities. A possible source may be the UN Statistics Division who I understand have a database on disability called DISTAT which they plan to make available on their website .

More websites on disability statistics can be found on the National Center for the Dissemination of Disability Research (NCDDR) website.

Were people with disabilities involved with the development of ICF?

Disabled Peoples International, European Disability Forum, Inclusion International and many individuals with disability were involved in the development of ICF.