If you don’t need a password to login to the wi-fi or if you ask and the hotel tells you the wireless isn’t secure (or they don’t know), it’s safe to assume it’s not secure. So yes, other hotel guests can intercept your email and other internet traffic with simple software tools on their laptops.
What makes wi-fi safe when traveling is a VPN, or Virtual Private Network. That’s a way to send all your email and web traffic through your own secure and encrypted network, away from the prying eyes of other hotel guests who might be using packet sniffers and other hacking tools on the local network in the hotel.
If you don’t have access to a VPN with the business you work for and want one, you can sign up for one yourself. There are many different commercial VPN services out there, but one that is easy to set up and use is WiTopia. It works with OS X and with Windows, too.
I think WiTopia’s personalVPN SSL for Mac is the best choice. Its not the cheapest of their products, but I think will be the most reliable.
Once you get an account at WiTopia and install the software, you can connect to the VPN service from a new icon in your menu bar. WiTopia has phone and email support, too, and online documents: Installing personalVPN-SSL on Mac OS X – Witopiawiki.
With a VPN, all your wireless internet communications while traveling will be secure.