Definitely take the Galloping Goose trail out to Sooke. West Coast Road (the main road to Sooke) is not a place I'd recommend for bikes.

Another scenic ride, branching off from there is the Lochside Trail. It's more or less the same thing, but going out the east coast of the island and onto a peninsula ending more or less at the town of Sidney.

Going around the waterfront is nice too. From where the clipper docks you just hug the water following the hotels and then keep going following the signs that say "Scenic Route".

If your in town on a Sunday, the local MEC (Canada's REI) offers group rides available to the public for free at 9am.