I bet that the department admin would tell you where you stand on the waitlist if you were to reach out. If you haven't already, I would be transparent with them and say where you are on (and what offers you have rejected).
Others may disagree with me here, but if you are serious that you will go if you get accepted at UCSB, I would tell them that. Particularly as we get to the end of the cycle, they may want to prioritize sending offers to people who they think will attend (as opposed to sending an offer to someone on April 14th, and not hearing about their decision to until the end of the day on the 15th).
