You need to put your actual available date.

Corporate guys like you are coming out of the woodwork all of a sudden, if they like your package they might well call you immediately. If you're honest it won't be an issue, they'll put you in the pool and hope you won't bother to interview anywhere else in the meantime.

But if you show up at an interview, where they expected and might be planning on you starting in two weeks, and tell them it's really six months... that would be the end of that.