I visited on 18th Nov 2023, as a day trip on my way to Solo airport from Borobudur. I went only to the main museum, not the dig sites. It's easy to get to - it's on google maps and the directions it gives are straight forward and accurate. At the museum we had to park some distance away and get a little shuttle bus to the museum. The Museum, about Homo Erectus aka Java Man, that was found in various digs around the nearby countryside was, pretty good. Nothing spectacular. The majority is written in Indonesian, but maybe 30% has been translated into English, too. After a few rooms putting the discoveries into greater global context, the 4th and last room shows you the actual fossils of Sangiran Man, including Sangiran #17 which is the best preserved skull. I couldn't actually tell if what is displayed is what is found or replicas. I assume what was found, but I couldn't be sure. 

If you're in the region, worth a morning detour, but I wouldn't plan a trip around visiting.