If you are having the devices report up to the Site Manager asset dashboard you can set the location for the devices.

Click on the Group, click on the user button,

Click on the username box to edit the user

Click on the Set Location button

Click on the Choose Location radio button, then click on the set location drop down menu to select the location the devices will be set in the asset dashboard, press OK to complete the setting

You will now see the location selected on the User screen