Do we have to post cut off times at the branch? It is in our funds availability disclosure provided at account opening.

You should talk to your bank's compliance officer about this.

Is there a reason why you wouldn't want it displayed? You know as well as I do that customers neither look at nor remember what was given to them (I opened my account over 15 years ago and cannot be expected to remember this). Why not have it posted so they know what to expect?

You should have it posted at your teller line and your drive in. This is a compliance issue as well as a customer service issue.