If you want a public wifi I would suggest http://open-mesh.com/store/. $50 each and the signal can be hopped up to 3 ap's, and all ap's can be centrally managed.
They are designed for public places like hotels. The problem I have with them is that they are actually routers so the laptops connecting to them get open-mesh ip address, which is not so bad but could cause some logging issues. The advantage here is that if this a just a public wifi there is a check box to isolate the open-mesh network from your current network so it is ideal for public wifi.
is another centrally managed ap solution. Mike Lambert would know more about them then I would.