This is all down to the Hardware you are using. I have 3Com Wireless Firewall Router Modem, and PCMCIA card. I was at My daughters boyfriend on Sat night and connected to next doors Belkin Wireless, I went to warn him about is Router not being Secure but he said to use it as He did not have a Download Cap, and did not need security.
PS it connected through about four walls across gardens. And HE WORKED FOR A BANK. So you know who to blame next time you info goes missing