I ride about 2 minutes from my house, in the Deas Slough. See the pics that Evan Park posted a couple of days ago. The Deas Slough is in Delta (Ladner). We usually have the boat in the water from April to October. Temp in the early and late season is in the mid 50's, and summer mid to high 60's, maybe over 70 if you're lucky. It's tidal water. I know people who ride all year round, but of course the boat would have to stay in a heated garage.
There are other places to ride, but they are further out. We used to ride in the Pitt River, near Pitt Meadows. There is also Allouette Lake and Cultas Lake.
Are you thinking of moving? Vancouver was just rated the "world's most desirable place to live", according to the Economist Intelligence Unit's livability survey.
http://www.cnn.com/2005/WORLD/europe/10/04/eui.survey/ The only thing they probably didn't consider in their survey was a long and warm summer