try
http://www.btopenzone.com/find/hotspots_explained.jsp or
http://www.thecloud.net/mycloud/ this is the sort of thing you need to be signing up for, be careful if you do it yourself with a wireless router, you will need to make sure it is secure you dont want all the people on henry St with free internet access do you?
Saying that, if you did do it yourself you would have to give the details for the paying customers so they could get access, they would come back then the day after and sit outside and use it unless you changed the log-in details daily.