I managed to find the setting to turn my browser to HotSpot Browser instead of UMA (t-zones) and YES!! How incredibly liberating now I can use my BB over the wifi network for UMA as well as browse the Internet over WiFi and NOT go through T-Mobile's UMA infrastructure which always wants me to buy an Internet plan.

I'm busy installing Google Maps etc ... so cool.

Good for you . . . I sure hope you know what you're doing . .. especially with Google Maps. You will need Blackberry data plan for Google Maps to work away from wi-fi connectivity. . .

Google Maps won't work even on WiFi ... so I'm working on that. But the browser works great.

Google Maps need to be "permitted" to connect to the internet. Check your permissions:

Options -> Advanced Options -> Applications -> highlight GoogleMaps -> hit Menu -> Edit Permissions -> make sure Connections/Interactions/User Data are set to ALLOW.

Nope, I had set all 3 to allow.... still get "network unavailable" ... I suppose it may be that I'm behind my home firewalls but ....

try this one:
OPTIONS -> ADVANCED OPTIONS -> TCP/IP -> APN Settings Enabled with check mark
APN: wap.voicestream.com -> save settings

How exactly was this possible. I'm still struggling. I have T-Mobile and "upsell" is one of my least favorite words right now.

Google Maps does not work without some kind of data plan. It won't work over wifi alone, as is evident by the posts in this thread.

To browse the web without a data plan but connected to wifi go to Options >Advanced Options >Browser and set the default browser to "Hotspot Browser" or "Wifi Browser."