If you want to send a message, not going to the polls is the worst thing to do. The best way to clearly send a message is to vote for a third party candidate. It would send more of a message that Bush has lost his conservative base if right wing third parties get 7-10% of the vote than if those unhappy voters do not show up in the election results.
I am, even still, a loyal Republican, even if the elected leaders of my Party are not. I am loyal to the conservative principles of my Party that have been abandoned by Bush, Schwarzenegger, and the host of devotees that follow them. I will vote Republican still: I will probably write-in Tom Tancredo's name.