Hey thanks for the responses. I am leaning towards a cable lock cos they are lighter and easier to use and I like travelling light, but I may still consider a U-lock--they do look heavy though. Is there a lock that I can wrap around the seatpost so it's not in the way? If you were to recommend a cable lock that's light, yet full functional, which one is good?
Again, I'd probably only lock the bike with a lock for a few minutes, while eating lunch at a cafe or something or to zoom inside a store. Maybe I'm dreaming, but the idea is that if I use a lock, the bike will be within my eyesight 90% of the time in case someone tries to steal it.