No, this DOES seem to be some sort of system-wide issue. BOTH my wife's iPhone 3G and my iPhone 3G could dial out, but no data. Even the AT&T "MyWireless" app doesn't work. Although I could get my "wireless bill" through the Phone Settings panel.
Just spoke with iPhone support in Orange County. It appears there was a serious "system-wide" outage affecting Los Angeles, Orange County, and San Diego. The tech I spoke with directed me to turn off my phone and power it back on. That restored Internet connection, but only briefly.
I suspect it'll be touch and no-go for a while...
UPDATE: Turning on AIRPLANE MODE for about ten seconds and turning it off again also completely restored data connection.