Wonosobo is a small city encircled by mountains in the centre of Java and overlooked by Mount Sindoro.
My suggestion:
It's not really necessary to spend time in Wonosobo being close to the Dieng Plateau, it's perhaps more preferable to stay there than at Dieng where the choice is very limited...
My review
The aim of stopping at Wonosobo was to break up the journey a bit between Borobudur and the Dieng Plateau, which is two hours away from Wonosobo. In fact the journey in bus can be pretty chaotic in Java due to the state of the roads (
crossing Indonesia and above all Java isn't restful at all!) and this will seem too tiring to come from Borobudur in one go.
In the end, it didn't prove to be a wise choice.
Wonosobo doesn't have any particular attraction apart from Mount Sindoro, which we see from afar. Around, it's essentially lakes and tea plantations. The city is calm, perhaps a bit too much. Even to find an open restaurant is complicated....In the street, we come across fruit sellers above all, no tourists (probably for the best). As for folklore, you can go on a trip in a horse-drawn carriage (even if they are found elsewhere in Java).
At least, the hotel where I stayed was really good ( the best of those I stayed in in Java) and it was at the end so I needed a good rest.