If you have an iPhone, I would read this article about Apple’s Safari browser exploit.  Best advice in the article comes from Mike Kershaw who wrote the open-source WiFi sniffer Kismet:

If I had an iPhone I would be very worried about using it out in public,” he said. The attacks might sound far-fetched, “I wouldn’t want to trust my company’s security” to the devices as they stand, Kershaw said. “One way to mitigate (these threats) is to turn off Wi-Fi,” he said.

To turn off WiFi on a iPhone, got to the Settings button and then touch ‘Wi-Fi’, at the bottom of the ‘Wi-Fi Networks’ screen flip the ‘Wi-Fi’ slider to off.  In my opinion, you can flip the ‘Ask to Join Networks’ slider to off which would stop those annoying pop-up messages to join a new Wi-Fi network and mitigate accidentally connecting to a malicious access point.