Seems to me that you should imply to every school you are waitlisted at that they are your top choice. I see no reason to be forthcoming, unless you think admissions committees from different schools are communicating about specific applicants (seems highly unlikely). Admissions people may realize this is "cheap talk" but I don't think it would hurt.
Having offers or even waitlists from other schools would marginally decrease your likelihood of attending, so I wouldn't mention it unless you can present it in a way that seems to increase your chance of accepting. E.g. "I am waitlisted at X, but even if they accepted me I would still be very interested in Y".
Don't lie, but play the game to the extent you can. Once you're in, you're in.
EDIT: softened my language.