If you're skeptical about LPWAN range claims .. better thing to do is to test :)
We (Sigfox) are running a hackathon in SF on Nov 20th, in partnership with the City.
Good occasion to test the live network, and get your hands on a dev kit
The Akeru board is still quite expensive (€100), as it's a full Arduino/Genuino board + sigfox module + subscription. And the guy is producing them himself, with small batches.
This one is not FCC-ready yet anyway.
Those dev kits are pricey... Is this the one? http://snootlab.com/shields-snootlab/829-.html