It will default to the location of the computer on which the Mathematica Kernel is running, if that can be figured out.

The symbol (dollar sign)GeoLocation can be set to your latitude and longitude. For example,

$GeoLocation = {37.76 , -122.4 } ; 

can be added at the top of your Mathematica notebook or in the Kernel's init.m file
(in the Kernel/init.m file under the base directory or userbase directory, as given in
http://reference.wolfram.com/mathematica/tutorial/ConfigurationFiles.html ).

$GeoLocation = {37.76, -122.4}; GeoGraphics[]

gives a map of San Francisco (in Wolfram Programming Cloud).

That is interesting. Are you talking about the Wolfram Cloud?

Note that you get different outputs depending on how you ask for your current location:

== current geoIP location

, i.e. using the double equal sign, gives you your correct IP address. This does work in the Wolfram Programming Cloud.

= current geoIP location 

gives the IP address a server that Wolfram Alpha believes is registered to Amazon, see:

http://www.wolframalpha.com/input/?i=+54.209.144.183

GeoGraphics[]

indeed gives a map of Champaign.

FindGeoLocation[]

in the Cloud gives

GeoPosition[{40.11,-88.24}]

which is Champain, I presume. On the RaspberryPi it does work as expected. Perhaps it is worth reporting that to the developers?

M.