If you're wanting the fax number to send over specific room requests, it probably isn't worth your time. According to folks on these forums, the DVC resorts don't handle requests the same way that cash resorts do. Your requests need to be specified on your reservation through Member Services. Faxes will be ignored.
I read not long ago on the official members site that DVC resorts do not accept room requests via fax anymore. We just note ours when we make the reservation.