This is my first portable WiFi gadget, and I'm wondering if it's doing what it's supposed to when trying to connect.

Just wandering around, I see lots of unencrypted routers, but am almost never able to connect to them. It gives either "Network connection error" or "Unable to obtain IP address". On some of these the signal strength is half a bar or better.

I have been able to connect to three out of the four legitimate WiFi hotspots I tried.

Is that normal, not to be able to connect to random unencrypted routers?

Is there anything I can learn from either of those error messages other than that the connection didn't work?