There is a small lot across from the Subway on Smithe and its around the corner from the McDonalds on Granville & Smithe. When you go into the garage there is a bottom corner rights as your going past level 1 so to speak. Depending on the time of day, other vehicles shielding you and other variables that are unpredictable you can literally fuck on top of your car if you wanted. It is an open access garage with the gate up but the way that corner has some angles/advantages to doing stuff. Stanley Park has what some would say has lots of opportunities but there are too many random hikers, joggers, tourist, etc. I got some action once where the Brockton Point Lighthouse at the lower level but way too many people was hard to focus. There is a small somewhat reliable parking lot on the Beach Ave entrance/exit side of the park in the evenings by the lawn bowling. Deeper in, not a lot of traffic, single lane, Can park facing away from the road. Adjust your mirrors to keep an eye out. On the weekdays, try the Canada Place Cruise Ship Terminal Parking lot. Go in and all the way towards the end by the stairwell that'll lead you up to the top but dont actually park at the end. You want to be close though.
The Royal Centre lot by Art Phillips is also an option for the evening. Avoid it during the day, too many car prowlers.
The back alley parking lot for Nesters Market on Main street a block from Tiger Spa....the lot is behind it, if you hit Quebec street you've past it. Park all the way down towards the end. During the day/early morning you should be fine. If your parked by the elevator your wrong lol.