Add a content type as a select list when creating a new user
If you use/add the Content Profile module, you can use it to create a profile for each user. In that profile content, you can have a field that is a node reference back to the Location type you mention.


  This module builds user profiles as content (aka nodes), which opens the opportunity to use all the powerful modules for content for user profiles too, e.g. the Content Construction Kit (CCK). It's intended to be simple and useful, but extensible by further modules.
  
  Content profiles can be restricted to certain roles; the module also supports separate content profiles for different roles.