Can my HMO force me to go to a doctor who forces me to sign away my rights to sue for malpractice,?

I have not seen a doctor for over a year in spite of medical conditions that need to be treated. I have to go through a designated primary care physician. His office has a recorded message. They do not answer the phone and say they will call back. When they finally do call back, they will not give an appointment for three months. I dropped by their office once and was told I would not be seen unless I signed an agreement not to sue the doctor for malpractice. Is this legal in California? Can I demand that the HMO allow me to see a doctor that does not require me to sign away my rights?