Adam:
In my opinion, which should not be taken as advice of counsel, and should not be construed as a legal opinion,1 the sign would, I imagine, do little to change the liability of the club to the surrounding landowners. A warning which doesn't mitigate the risk, or alter the dangerous condition to the surrounding property owners, either created or maintained by the club, is really no warning at all, at least from the surrounding homeowner's perspective, no?
But then again, if I remember correctly, you are from Canada, right? I know very little about this sort of thing from an American standpoint (contrary to David Moriarty, who believes I know nothing), and I know far less about it in the context of Canadian law (approaching David Moriarty's estimation) - but rest assured, however the Canadian courts view this sort of thing, it is bound to be eminently more sensible than how it is viewed by their American counterparts.
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1.disclaimer added for the benefit of, and protection against, David Moriarty, Esq.