Brockton is a fabulous 400 meter, black-cinder surface, oval that can be used for running fartlek sessions and intervals, or just a more measured jogging session. There are bathrooms there as well. Check out the linked map to see where it is in Stanley Park, but it's not too difficult to find.
Group runs also go out from here on Saturdays at 9am (Vancouver Front Runners) and they welcome visitors.
Directions: Make your way through the main entrance street of the park and past the information booth. Veer left onto Aviston Way - take the Brockton Oval Trail on the right and it will bring you to the track after about a half mile. Or, if you follow the waterfront path, once you see the totem pole, look away from the water and you'll see a house -- the track is just beyond the house.