That's difficult to say, since what works in one area is different than another! For new areas, I
I'd recommend two ads, one about 9 or 10 days in advance so guys have plenty of time to check out your profile and reviews and then a reminder ad 2 or 3 days before you arrive.
I think vic's advice is good. Another thing you might consider is making yourself known on the local board - just reply to a few posts, and you might get a chance to mention that you'll be coming to town and hope to meet some of the local guys.