EDGE data service (Enhanced Data for GSM Evolution, not to be confused with the cell phone carrier Edge Wireless) isn't what I'd call high-speed, only up to a maximum of 200 Kbits, and averaging around 150. Still, it is much faster than a modem. I don't know what kind of data plans Edge Wireless may have, but I do know that Cingular puts some vague download caps on their plans.
There's also EVDO, which is offered by Sprint and Verizon, though the latter has a 5 GB per month download cap. If you can get Sprint EVDO coverage in your area, even if you have to mount an antenna on your roof, then you're golden: Sprint offers truly unlimited service, with peak speeds above a megabit. It's the closest thing that you can get to a traditional broadband experience via wireless.
There's also Cingular's high-speed network, but it's got a lot less coverage area, so you're less likely to be able to get it.
One last thing that you might actually look at is a T1 line, or find out whether your phone company might offer EDSL (which is similar to a T1, but a cheaper alternative for a residence). It would be expensive, certainly, but some providers will give you a T1 for $400 a month, and if you can split that cost with your father's employer, it might just be worth it, particularly when you consider the amount of guaranteed bandwidth that your father would need to download his files. EDSL isn't guaranteed the way a T1 is, but on the handful of companies that offer it, it does tend to be substantially cheaper.