All the tickets say "non-transferrable", but that is totally non-enforceable. What you are doing is fine (and I have done it before).
I am an annual pass holder, and they give me a discount on additional tickets ... what else would I do with those tickets besides "transfer" them to someone else?
The signature thing is for Flex Tickets, and they are supposed to be signed and you sign a log at some parks also when you enter, though enforcement is lax it seems ...