I realize this imposes some costs on you, but I'd recommend that you just say you're going to be at a place and time with a sign, and that people should come. This avoids the whole "I'm not sure I should come because everyone else might not come because they're not sure..." cycle.
You might want to choose the date/time based on feedback here, but honestly I've had a lot of trouble scheduling meetups based on feedback about time, and I eventually just started dictating meetup times.
I can't make it this time, but I'll be moving to the Ann Arbor area in June and hope there will be more meetups then.
Oh, sorry, I only just saw this. Uh, maybe? Whenwhere would it be?
You might want to actually add the meetup on the meetups list, maybe you'll get a few more people that way.
Tentative date: either Saturday, May 11 or Sunday, May 12 (2013). Is anyone interested?