I realize that this post is quite old, and that we've been in touch (and done some canyons!) in the meantime, but I wanted to respond to the points raised here. Someone in the future may read this and have the same questions...
There are no actual teaching or guiding groups that I'm aware of in the local area. About the closest way to receive instruction is down in Washington State, through ATS: http://www.theatsteam.com/adventureworks/index.html
. They are based in Los Angeles, but do some training courses in Washington, east of Seattle in the Snoqualmie National Forest. However, they had advertised a three day course at the end of August, 2013, but didn't receive enough interest and had to cancel it...
The best way, right now, to get out and try the sport in this area is to go with experienced canyoneers. And the best way to do that is by networking.
First off, this forum is mighty slow, but I'd sure like to see it take off and be a place where people can get in touch with others who have the same interest. I like the idea of a forum like this, rather than a group on Facebook, for in depth discussion, trip reports, etc.
But, speaking of Facebook, there is a Vancouver Canyoning group there, where you can post to try get in touch with others. What might work the best is to post a brief introduction, with your experience in ropework (climber? mountaineer?) and other outdoor pursuits (kayaker? backpacker? diver?). You likely won't get any invitations directed at you from an intro, however - your best bet is to watch for people posting about planning a trip, and inviting others to join them. The Vancouver Canyoning group is here: http://www.facebook.com/groups/485642308115596/
Personally, I like to take new people out and do canyons, sharing my love of the sport with them. This year, 2013, I have taken around ten people through either their first technical canyons, or their first flowing technical canyons (after doing limited numbers of dry canyons elsewhere.) So watch for me (Kevin Swanson) posting open invites on the FB group, or here.
Keep in mind: Canyoning can be a dangerous sport. There are inherent risks. Be certain that you are not going out with inexperienced people. Your safety is your responsibility - if you have any doubts about your safety, call it off. Consider getting professional instruction in basic ropework, if you have no experience with anchors or rappels (i.e. through rock climbing).
An Introduction to Rock Climbing course for absolute beginners, combined with a course in top-rope anchors will lay a good foundation. (If you've done some gym climbing, skip straight to the top-rope anchors.) I did a top-rope anchor course with Squamish Rock Guides
many years ago, and can highly recommend them. I also have been involved with the BC Mountaineering Club
for the past ten years, and can strongly recommend a mentor-type program with them as well (or with the Alpine Club of Canada