Is the road to Alishan open?
Yes. No problems unless you are driving a large bus. Explore around.
Should I go?
Yes - especially now when few other are, and before the summer rains cause problems. See the blue truck below? Looks worse than it is...
Any other good suggestions?
Go (if you have your own transport that is) hike the various scenic trails around Tataka (Tatajia/Tatachia), 20km beyond the developed forest recreation area (FRA). Suitable for a few hours or 1-2 days. Quiet. Very quiet from mid afternoon. One of the views of Yushan from Tataka.
And the train?
The famous forest train line from Chaiyi to Alishan is in a bad way. Locals say if the government spent enough money on the best experts and technology it could be running again within a year. Short routes in the FRA fine I think.
The Danayigu fish place is gone.