Hey there, my friends and I will head out to Yilan next week. Does anyone know any nice beaches in Yilan or nearby? Thanks! 
Hi Anniecsh,
You might find answers to your questions in this thread: https://www.forumosa.com/taiwan/viewtopic.php?f=25&t=132131
The most popular beach in Yilan is at Waiao or Wushi Harbor. Lot of surfing going on there, and lot of people on summer weekends. If you want to avoid the crowds, Honeymoon Bay, further north was once the place to go for surfing fun, but nowadays there are not that many people.