If we're talking about a data-only plan for a laptop, AT&T is 200mb for $35 and 5 gig for $60. And IIUC if you have the modem and it's on the right frequency, all you need is the sim card.i will be in san francisco city all the time. Thank you very much for the links! but AT&T doesnt seem to have prepaid data (via your link).
its so easy if someone comes to austria and wants mobile internet hes just to go to a discounter and buy for example a "yesss" data packages. 1GB for EUR 20,- prepaid, no contract, no activation fee, no registration. just the sim.