When using an https:// connection through your Web browser, your personal information is protected, even on otherwise insecure connections. This is generally considered strong enough network security to have when sending your credit card number, for example. At a public hotspot, the greater risk is usually someone situated behind you able to see the numbers you type.
Another security risk on public hotpots involves other computers also connected to this unsecured network. Network attacks can be made through them, by connecting to your computer and possibly downloading information from your hard drive.
People address this latter problem by running a firewall program on their computer. Firewalls guard against these incoming attackers. It is additional considered good practice not to stay connected to unsecured networks for too long of a time to become an attack target. You should always run a good firewall program whenever connected to a "unsecured wireless network" and disconnect when not using your link.