AT&T Wireless will have Unlimited Data soon!
I called AT&T this morning to increase my data amount on my wireless plan. I bumped it up to the max (8 MB) so we could do choose our hotels as we go (using GRPS and our PowerBook). The lady put me on hold for a minute to two, and then came back with "actually, there is the Unlimited Data plan you were looking for - it's $24.99." I said - "hook me up!" But when she tried to select it, it said "not active." So it's in AT&T's system, just not activated. Cool!
Another tip she gave me when road-tripping was when you receive "No Network" - turn the phone off and back on so it can re-initialize with the nearest tower. BTW - how is AT&T's GSM coverage in California?