Well, a firewall on the road isn't going to do you much good, especially if you are planning on picking up email from your ISP etc...

Unsecured WiFi can be intercepted VERY simply, and unless you have any kind of file sharing turned on there won't be any open ports on your laptop that will be of any use to a hacker.

So, focus more in the central side (your email etc...) and consider either setting up a simple VPN at home or asking if your ISP supports secure pop connections. A firewall looks nice and reports a load of attempts, but unless you have something open on your machine then the WinXP firewall will be more than sufficient.

But when zonealarm is doing it's best to prevent "hack attempts" someone else is snooping on your unsecured WiFi connection and has your POP password and is reading all your email...