Covad provides DSL service primarily to business users, and also resells DSL to other ISPs. I would highly doubt that they will get any closer than 14k feet if that's what other DSL providers are telling you.

Regarding broadband, you could go sign up for it, try it, and then return it if it doesn't work for you (or your budget.) Ask for a USB based antenna.

I'm a Verizon broadband user and its fine, but a lot of FT people are hot on Sprint. The general feeling is that Sprint is doing a lot of infrastructure investment for their future in WiMax - a next generation thing you don't have to worry about.