Most folks think about others breaking into their WiFi network, vs what others can snoop from your network. The solutions are MAC filtering or WEP or WPA. Even though they all will limit traffic going IN, only the encryption protocols will protect it from local snooping. This is a good reason to run VPN across Wifi.
I was curious what I might see using my ethernet protocol analyzer software with my Wifi connection. It appears the transmitted traffic is just like a hub. I can see the network traffic being transmitted from my neighbor's non-wep AP.... So, just remember that when using a public AP, anyone can see what traffic is being sent from the AP back to your laptop.