Just a small note to complement Ken's excellent information (thanks Ken!).
Moodle only redirects the user to the profile page if the first name, last name or email is not filled in (either directly by the user, or obtained from and external source like LDAP). So in this particular case mapping the firstname, lastname and email fields would be enought.
In fact, if you are using Moodle 2.2 or later, so can set a default country and city for all your users, that will be used if they don't specify one (or is not obtained from external sources like LDAP). You can set these defaults in "Site administration >> Location >> Location settings".