I'd start calling around now, ask what their wait lists are like, etc. Can't hurt to start early but you'll regret starting late if spots are seriously limited in your area!
I'm in the east end and visited the place we ended up going with when I was about 30 weeks pregnant with ODS. I put my name on the list and they called when ODS was about 5 months old to offer us a spot for him when he turned 1. I had my name on another list (visited just after ODS was born) and still haven't heard back from them
I called them a few times and there were never any openings.