Just one thing to make sure of before you get on the trail. When I was there last August I just happened to find a copy of the West Coast Trail Shuttle Bus time schedule at the Hosteling International Victoria youth hostel. There were also schedules posted on the signs along the trail, but the information was several years out of date.
Also, if you want a detailed map of the trail try to get a copy of the book "Giant Cedars, White Sands: Juan de Fuca Marine Trail Guidebook" by Donald C. Mills. It has the most detailed (but still rudimentary) map of the trail that I was able to find in Victoria. MEC and Robinson's Outdoor Sporting Goods Store, and the other hiking specific stores in town all didn't have any good maps of the trail. However, if you go to Ocean River Kayaks along the harbor, they had the book above and some very helpful and experienced staff members who took lots of time to give me firsthand advice for the trail (Well, the staff at MEC did, too).