Much thanks to the awesome support and guidance - have optional search field working beautifully, and also have an ANY or ALL field for the combobox.
For the combo box query I used the following, which results in an Any option to be listed in the drop down along with all of the available regions.
'Any' AS SearchOption, '' AS SearchOptionValue[Text] AS SearchOption, [TEXT] AS SearchOptionValueLists
WHERE
ListName = 'Region'
I also needed to enhance this a bit to only list regions where contacts were available... this is a bit quirky, and there is probably a better option like using a JOIN, but it works swimmingly.
SELECT
'Any' AS SearchOption, '' AS SearchOptionValue
UNION ALL
SELECT
[Text] AS SearchOption, [TEXT] AS SearchOptionValue
FROM
Lists
WHERE
ListName = 'Region'
and [Text] in (select distinct [PropertyValue] from UserProfilewhere PropertyDefinitionID = '28')
FROM