And that is certainly your right. However you stated you were planning to write in Palin and asked if that is considered not voting.
The answer is yes, that is effectively not voting. Palin is not a candidate, can not be elected President as a write in, and does not want your vote. Unlike yourself, Sarah Palin is supporting the Republican candidate and probably wouldn't appreciate you trying to cancel out her vote.
We all do what we believe is right.