I think we need to clarify some of the terminology that's out there, otherwise the advise you're getting isn't going to make sense.
3G: wireless and provided primarily by cellular phone companies. Data can be accessed over a 3G connection by either using a 3G capable device OR by using a 3G hotspot, which upon receiving the 3G signal will than rebroadcast it as WiFi. The 3G hotspot acts as a sort of intermediary between a WiFi capable device and a mobile phone companies 3G network. For instance, when the iPad first came to Verizon, buyers needed to purchase the WiFi only model plus a 3G hotspot device in order to use Verizon's data network because the iPad did not have the correct 3G chip installed. Although you may be able to find a cell phone carrier with a better 3G network than what is provided for the Kindle (Amazon contracts with AT&T), purchasing a 3G hotspot will NOT save you any money as it would require a monthly data plan with a cell phone carrier.
Wifi: Generally, the telephone or cable company allows you to have a data stream along the same physical lines as your phone or tv. You can then use a wireless router that will allow your WiFi device to access this data stream over the air.