IMPORTANT NOTE: there will be people trying to grab you to go with them on the boat to Yangshuo, they might say that they can take you from Guilin to Yangshuo with a 1-hour long boat ride, please do NOT go with them. We made a mistake and went with them and turns out it’s a scam that you get a less than 1 hour bamboo boat ride in between a 1 DAY trip booked with them with ENDLESS bus rides, stops you’d have to go shop at and places that they said it’s cheaper as you’d not be purchasing the national park tickets, which is a lie. (We met 9 others on that tour that got scam too and they kept trying to make us buy tickets to see the shows… the shows aren’t great and quite fake so I don’t recommend it)
On the other hand there are 2 boats that actually go from Guilin to Yangshuo which lasts for 4 hours and the last one is, I believe, at 11am. So if you’d really like to, get onto that one. The boats are more like cruises on these and the scenery is gorgeous, just long… so if you’d really like to visit Yangshuo on a bamboo boat, I’d recommend doing it at a sight you really like but locals actually recommend hiking around a bit to see the view.
Anyway, hope my advice help. Yangshuo is a wonderful place to visit, I’m dreaming to go back soon! Enjoy!