How can I change the case of all contacts' cities?
I put together the following Applescript that solved my issue. To get titlecase function, I downloaded and installed "Satimage osax" from http://www.satimage.fr/software/en/downloads/downloads_companion_osaxen.html.

tell application "Contacts"
    set All_Contacts to every person whose name contains "test"
    --set All_Contacts to every person
    tell me to display dialog "Are you sure you want me to correct city of " &amp; (count of All_Contacts) &amp; " contacts?"
    repeat with My_Contact in All_Contacts
        set All_Addresses to (every address of My_Contact)
        repeat with Current_Address in All_Addresses
            set city of Current_Address to (titlecase (get city of Current_Address))
        end repeat
    end repeat
    save
end tell