Hi Liz
If you have the location information structured in an organization hierarchy you can Select the Content tab in the report and Select the 'Show by user's current organisation ' The report viewer would then only see records of users that are in the same organisation (or below) as they are.
It is also possible to select 'Show records by audience' to give more control of who you want displayed in the report using audience rules to select the users you want to display. This would mean a different audience and report for each location so the technique above is preferable as only one report is required.
Regards