C-Train is the way to go. Don't take your car anywhere near the Stampede. Parking is very expensive in private lots and it is pure misery to try and get out of the area.
If you decide against the C Train and don't mind a fifteen minute walk you can drive just East of the Stampede grounds into the community of Inglewood. (9th Ave area) On residential streets parking is free and easy to find. It is a safe area to walk, even at night.
Cowboy hats and big belt buckles are mandatory during the Stampede so make sure you are properly equipped. It is a fun time in a great city.