lets be clear on this: it means NOTHING if you havne't been called. First, under the table stuff is illegal and believe it or not, many people follow the ethic and wont do it (and you might certainly be inclined to take something if offered, but keep in mind that a person who violates the ethics of the system, well its something to keep in mind.
Some people can sign out of the match but the program must withdraw that space from the match. Outright. Generally IMGs get that option but not exclusively (and the details are beyond me).
As for being told youre being ranked "number one" etc, its worth the paper its written on. I know more than one person told that who subsequently didnt match. Its fine to communicate and have communicated to you that a program is interested but promised rankings mean zilch and and its ILLEAGAL to ask you where you'll be ranking them. If asked, you can express your great interest and obviously dont shoot yourself in the foot. but keep in mind, this is not what is supposed to be going on.