You'll need a table of locations where you have one record for each location in order to base your layout on this table instead of your portal's data.
This makes it possible to set up this relationship:
Locations::Location = PortalTable::Location
and two calculation fields cTotalMambers and cTotalguests can then compute the totals for each location:
sum ( PortalTable::Members )
Sum ( PortalTable::Guests )
Now you can set up your bar chart with two Y axis values ( cTtalMembers, cTotalGuests ) and Location will serve as the x Axis to label the data.
Additional details can be built into the above relationship to limit the data to a specific sub set of all records in your portal, such as just those for a given date range.