Do you mean that you want the values in your value list to be in this order? It doesn't seem that you are actually sorting the database.
If I have that correct, is bp_placename_index the second field of your drop down list's value list? If so, you can sort on it instead of the Key field value. If not, then you cannot. Value lists that display values from a field are only shown in ascending order--with the values of either the first or second field specified as the "sort" field.
To get a different order would require using a different value selection method such as a selection portal placed inside a popover.