You may not know it yet but you can dictate to Siri in different languages by using the international keyboard for that specific language or by changing the language Siri currently uses and selecting the one you want to speak in.
Setting Up An International Keyboard For Siri
Just go to:
Settings, then select Keyboard, then select, International Keyboards, then select, Add New Keyboard
Changing The Language Used For Dictation
Just tap the globe icon to switch the keyboard for that language, then tap the microphone icon to start the dictation.
That’s it – cool or what?