I´m pretty sure it will be bilingual - German and English. But nothing on their website.
What´s also a bit weird... they are offering 3, 4, 5 night trips (out of Vienna and Budapest) - which in general is a nice idea. But...not worth the travel for an American/Canadian/Aussie. And even from Europe (inkluding UK) you need to fly and than it´s not worth booking. Even with the cheapest category I would end up with 2,000 Euro at least for a 3 night trip.
steamboats