We'll be in Singapore in mid-Feb for 3 days (our 4th visit) and want to explore this island Ubin by rental bike. Any suggestions on how to use public transport to get there? Best in morning or afternoon? Ideas for special places to visit? Also, are there any special events the weekend of Feb 13-14? The STB guide still lists January events.

We went to the boat pier by car so sorry I can't help with the public transport.
I would go in the morning as it does get very busy at the weekend.... Check you bike carefully, some of them are useless, make sure you test it out! Take plenty of water.
I really enjoyed our bike ride round PU !!!

We took the MRT, then a taxi. Had a lot of fun biking. Do check the bikes. We had to test several, and had to go back for a lock. Found the best prices at one of the spots farthest from the ferry landing.
It will be hot, so I'd recommend going in the morning. You might check the tide charts though. We felt the overwater walk would have been better if the tide was low.

Thanks folks for some useful tips. We'll head over in the morning and check out the bike rental place farthest from the pier. One other quick Q: What do you think about us spending a half day later at Dempseys Hill? In 3 previous visits I have not made there yet. We enjoy history, photos, nice casual food and quirky (non-mall) shopping. Thoughts?

You won't really get the history at DH, I like the "antique" shops there ( nearly all the shops there are "antiques" or homeware (there are a couple of other types) and they do have a few restaurants there ( you could go for the fabulous and famous) black pepper crab at Jumbo at DH.
You could actually combine that with a visit to the beautiful botanical gardens..