Gina - I know what you're going through. I remember being in the ICU and actually dreading visits from people, as I knew what it would take out of me. And then during treatment I had enough trouble just getting out of bed, let alone answering the phone.
Some great suggestions here, wish I'd thought of them!
I especially like the long stare.
But the assigning someone to be your PR person is really a great idea. Caring Bridge is also an excellent resource.
Of course, there are other less polite ways to deal with it too... (only half-kidding here, btw)
Remember that we're here for any and all venting!