It is one way trip. The Lijiang River Cruise starts at around 09:30 and lasts around 3 to 4 hours. You can back to Guilin on the same day. But Yangshuo is a very beautiful village. It will be a big pity if you have been there but without a visit. You can get the shuttle bus back to Guilin on the next day. And the bus tickets could be purchased on the reception desk of the hotel in Yangshuo. It is very convenient. The ticket is about 25-30RMB per person.