I just saw your question and I'm sorry to respond so late. Hopefully this can help...
I posted this a little earlier today:
"I've been using AT&T/Cingular and Verizon Air Cards for some time all over the world and have had pretty good luck with them - if you're the lucky type, you might be able to get the card for free if you can find a monthly service plan that doesn't hurt too much...
A better card is the one Sprint offered - much higher speeds than EDGE can get you - burst up to 600Kbp! However, if the 100-150Kbp doesn't turn you off (and certainly there's an understandable trade-off for your location being without DSL/CM), then you're going down the right road."
With that said, I have successfully used the Sony/Ericson EDGE Air card all over the US - the speed won't set your hair on fire, but as I mentioned to r00ster in the earlier post, it's better than no connectivity at all. The cards can (and on occasion have) cost nearly $400 - this is my experience. However, since this has been the case, I have seen many of these devices given away by service providers in exchange for roping you into a service agreement (one to two years). I've paid as low as $60/month with unlimited use for the EDGE Air cards and slightly over $90/month for the Sprint offering - even though this option costed more, it was worth it for the speed and coverage from NYC to SF.
Whatever you do I wish you the best!
Best cheers, Robbie M