Do I have to sign the evaluation if I dont agree with it?
If they insist that you sign it,
you should sign it -- refusing to do so would be considered "insubordination."
However, signing it does not mean that you agree with it, so there
is no reason to get into a fight with your supervisor over it.
When you sign, you should indicate that you disagree with parts
of the evaluation right on the form, and that you will write a
response. This way, your disagreement becomes part of the evaluation.
Then, prepare some very brief, coherent, clear responses. When
you send them to your supervisor, also ask that they be attached
to the performance evaluation. Your supervisor is required to
include your response in your personnel file.