Go alone.

I would go to Hungary, but leave him in Australia. You are going to visit family, not so much to sight-see, so he would spend a lot of time feeling left out and/or like he was intruding (and your family might prefer to see just you). If he doesn't speak the language, he'll feel especially lost and excluded. You would have to spend literally all your time with him so that you could interpret; few things can kill a new relationship like spending too much time together. Think about how much you and he will have to talk about when you get back and have spent some time apart and had separate adventures. A month seems like a long time, but really it isn't. You'll be busy and the time will fly by. If he doesn't come, arrange for him to pick you up at the airport when you return; super romantic!