Doesn't the output of the Google Geocoding API return the full address?
According to Google:
Geocoding is the process of converting addresses (like "1600 Amphitheatre Parkway, Mountain View, CA") into geographic coordinates (like latitude 37.423021 and longitude -122.083739), which you can use to place markers or position the map. The Google Geocoding API provides a direct way to access a geocoder via an HTTP request. Additionally, the service allows you to perform the converse operation (turning coordinates into addresses); this process is known as "reverse geocoding."
Emphasis mine.
The XML response seems like it does.
<formatted_address>1600 Amphitheatre Pkwy,
Mountain View, CA 94043, USA</formatted_address>
<address_component>
<long_name>1600</long_name>
<short_name>1600</short_name>
<type>street_number</type>
</address_component>
<address_component>
<long_name>Amphitheatre Pkwy</long_name>
<short_name>Amphitheatre Pkwy</short_name>
<type>route</type>
</address_component>
<address_component>
<long_name>Mountain View</long_name>
<short_name>Mountain View</short_name>
<type>locality</type>
<type>political</type>
</address_component>
...
if not, you could try using the Google Directions API.
Part of the XML output, as well as the JSON output, includes addresses. Here's part of Google's example XML output.
<start_address>Oklahoma City, OK, USA</start_address>
<end_address>Los Angeles, CA, USA</end_address>
I don't know if you would have to make up one of the addresses, or if you could calculate a route with the same start and end point.