A majority of cafe and other public area wifi routers do not have client isolation, so one way to deal with congestion on these networks is to connect to them and then do some arp poisoning to turn your favorite Android-based device into everyone's new router, and then selectively kill the worst bandwidth hogs. "There's an app for that", as they say.

...at least, that's what I've heard.

Android offers a surprisingly good toolbox for diagnosing and abusing wireless networks.