How can I be sure that my airport ext. card's working when I'm offline?

you could always try the hardware test cd that came with your computer. i'm pretty sure there is an airport test in the suite of things it looks at.

where was this hotspot you could not connect to? are you sure it was not one that required some sort of subscription? also, do you have your airport set to automatically find a location and get an IP? it could be that you had things set up wrong, and the airport card was not being told even to try to connect.

AirPort troubleshooting

I don't know if you can test your airport card without being connected, but you can probably go back to the same cafe with wireless hub and try to connect again. (just be sure that your computer actually supports airport extreme - the earlier models need the older airport, and the cards can NOT be substituted for each other)

Even if you can't connect, just finding a signal at the cafe will tell you that the card is working, and the problem is getting the settings correct.

NOTE: Following comments are from my OS X 10.3.3 - not sure how many differences there are from 10.2 if you're using that.

When you are at the cafe, look for the AirPort icon on the upper bar next to the time and your battery icon - it sould look like 1/4 of a circle. Click on it, and make sure AirPort is is turned on. Also select "Open Internet Connect" to see the status of the connection. (I believe you can also connect to another wireless enabled computer via this dialogue if you want to test your AirPort Extreme card.)

If you don't see the AirPort icon on your menu bar, open your System Preferences (Apple Menu) and choose Network, andelect "AirPort" from the Show choices.

Here's a link with some general (non-Mac) troubleshooting tips for wireless networks.

http://www.oit.umass.edu/wireless/tips.html

Good luck.

I think the question you have is how to find out if you are connected to a Wi-Fi hotspot.

MacStumbler and iStumbler will alert you to when you enter into a Wi-Fi zone.

You can also enable the Airport Icon on the toolabar and that will show signal strength...