If it's your own network, clear all network connections. Reconnect. When it asks about remembering your's click Yes. That should stop others from even appearing if your own network is on autoconnect.
I have 3 neighbors with wifi connections that my Evo doesn't even ever show. I see them live on my iPodTouch2G every time but never on my Evo.
It could be that when you get within range of your own device (also in range of neighbors), it's showing them because yours isn't already auto-connecting.
The open network icon might indicate that it's detecting the other network first and attempting connection there so even though you get back to your home network those networks are still available.