Most hotspots use equipment that keeps all the users in their own separate virtual space, so you won't be seen by others using the same hotspot.
I would like to see some clarification of the quoted statement, since that certainly isn't my impression of most public hotspots that do not require a password or have WEP/WPA enabled. Many hotspots use the same kind of wireless gateways as average users. In most cases a significant amount of sensitive information is sent in the clear and can be intercepted with relative ease.
The best security when using a public hotspot is a Virtual Private Network or VPN. The simplest way to take advantage of this technology is to subscribe to a public VPN, such as PublicVPN.com. You can subscribe by the month for $5.95 or $59.95 per year. It is simple to configure, VPN is supported by Tiger so you don't need additional software, and it is as secure as you can get.
Once your account is set-up you can elect to subscribe only when you need the service, such as when you are traveling. Charges are based on a 30-day period, not usage. You can also use VPN at home and it will provide a level of security greater than WEP or WPA, plus you avoid some of the configuration hassles some Apple users have when using non-Apple wireless gateways.
And don't assume that public "wired" networks are more secure than wireless. A wired network in a location such as a hotel can also be used to intercept data by others connected to the network.