The wire that you are now 'less' is the one between your 'puter' and the wall that ties you to your Internet Service Provider. Not the AC electric power wire. When you pick up those other networks, they may or may not be (hard to imagine 'not' these bays but …) connected to the internet via their ISP. IF you get to join their network, then you should be able to use their ISP and connect to the internet.
But, just as lotsa folks don't lock their doors, lotsa folks don't lock those nets you picked up. That doesn't mean you're welcome. In fact they might see it a sorta like burglary, and their friends (like their ISP) might helpfully not open up without a password, even if the naive net folks themselves do.
On the other hand, places like coffee bars often do welcome the laptop-using-coffee-buying crowd both in their shop and on their net. The Starbuck Strategy's a good one, and other laptoppers are quite likely to try to help out. Like TERBies.
