I know almost nothing about health insurance issues and laws but I'll go ahead post anyway and probably make a big fool out of myself!!  I could be wrong, but I don't think the health insurance portability law applies if you are self-employed or work for a small company.  After all, if a small company was required pay insurance premiums for an employee with a really serious medical problem it could easily bankrupt the company.  So while you definately should check into it, I think Blue Cross probably has the right to ask you to sign the waiver.  (Maybe you could check with an attorney first?)

One thing to think about, medications, lab tests and endo visits would not be covered.  But if your child had to go to the ER for a vomiting illness would that be covered since the visit was for vomiting, not for CAH?  If so, maybe the waiver isn't such a big deal.  If not, it would make me nervous.  Like everyone said, read the fine print carefully.  You wouldn't want them to be able to say every time your child went to the doctor for an illness that it was CAH related.

Good luck!