Question: Wouldn't phone calls to Fox execs be more productive if they made them laugh instead of angry? I know if I received countless annoying phone calls, I'd be more inclined to look for ways to cut out the source so that the annoyance eventually goes away. Put some wit and thought into it, and I think you'll help the cause. I believe that these are people who want to be convinced to keep AD on the air.
If sending bananas (real or fake), include the message: "Don't be a banana-grabber. Save Arrested Development." Note: The fake bananas also remind me of the fake food circulating around the Bluth house.
Also, put smears of blue paint on the envelopes, letters, bananas, etc.
I like the idea of refrigerator magnets with a note requesting they save A.D. - just like the notes George Michael always leaves. The magnets could have pass-around value.
I guess sending big yellow joints might send the wrong message.
How about sending fake eyebrows, with the message: "Cancelling Arrested Development doesn't Sitwell with us."