My wife and I hiked up to the Hill of the Cross when we were in Cesky Krumlov in late September 2014. The view was not as good as we had expected. Over the years the trees have grown, and while you can see the castle and the tops of the buildings in the old town, only a very small part of the river can be seen. Its hike is up hill for most of the way, and the path has become overgrown and is hard to follow. The stations of the cross are crumbling and the church at the summit is boarded up.
If you are pressed for time, I would skip this hike, as it will not be a good use of your time. Instead spend your time visiting the the Baroque Theater in the castle (very interesting especially if you attend theaters in your home town), or find a patio beside the river, grab a beverage and do some people watching.