Does Natural language understanding work with any other languages besides English?

I’d like to extend this to Spanish - is there a way to use Watson for Spanish NLU?

Indeed, Watson can detect language but there are several other considerations which should be noted.

    For NLU there a list of detectable languages, NLU work with any of these if you use chat interactions - it will automatically detect language like the following:

    This small smiley represents sentiment of the message which we het from NLU. As you can see it works correctly for 3 languages.

    If we are talking around voice part of the question then the list of supported languages is quite narrowed. So first we need to tell the Watson Speech to Text that we talk with him in Spanish for instance, this could be done by Set Language Block like below:

    From now and forth we will be sending a specific attribute to STT service that we talk in Spanish with it.
    And in Interaction Record you will see the same smiley later.

Spanish Traditional in our system is the same as Spanish (Castilian, es-ES) . Please let me know if any further help required.