This is purely speculation, but I think you'll be able to, based on how the UI under the network settings page was changed.
It was originally a simple toggle for having 3G turned on. It's been changed to a drop down box, allow you to select 3G or Edge. I'd assume LTE Windows phones will have an LTE as well, allowing you to jump down to running only as high as 3G.
Nolate in the year 1st part of the next year but is fixing to be up and running soon just to the north of my location soon. Primarily because of Wal Mart's home offices about an hour north of here. So when I go up there I would be able to check out the speeds and hopefully be wowed!