I can confirm first-hand that it is not particularly difficult to snoop on unsecured wireless traffic. The chances someone will snoop on you are probably close to zero, but if there IS someone snooping, the chance your data will be in an immediately usable format is extremely high.
You can avoid this issue by not connecting to unsecured wireless networks. Unsecured means unsecured. While it's true that any network could be compromised, that is not the same as saying encryption doesn't matter. With an unsecured network there's nothing to compromise - it's the equivalent of standing on a chair and shouting whatever you are doing at the wireless access point you're connecting to.
If you must use an unsecured wireless network, then only use it to do things that you would feel comfortable doing in direct view of strangers who are actively recording you while you do whatever you are doing. If that makes you feel uncomfortable, it should. Also take note that many devices will helpfully remember any network you've connected to so they can immediately identify the network and connect again without asking you later. If you do have to connect to an unsecured network, remove the settings afterwards.
Finally - an unsecured network is generally a network that not only uses unencrypted traffic, but also tends to use the default router admin password, the default SSID, default security (or lack thereof), old and outdated or buggy firmware, etcetera. This can make it easy for devices that should not be able to communicate across the network to talk. And while I am sure your device is secured, a maintained, secure network is another layer between your data and someone who may not have your best interests in mind.
