I believe city code states there is no parking in the alley's at all. Try going at it from that direction, having some tickets or their car towed might influence their parking behavior.

Thanks for reporting! If access to your garage is being blocked, please call the Police Department so it can be addressed immediately.

Thanks for fixing this issue!

looks like problem has resolved with no need for intervention. thank you for suggestions. I do understand renter's need to protect their 'horse'/ means of transport to job. Short of sleeping in car, and with a gun for personal protection, some live check to check where debilitating vandalism can be the straw for the camel. I've been near there. A parking ticket can actually be cheaper than replacing wheels, slashed tires (which void costco warranty) smashed windows, stolen vehicle for joy ride. A light sleeper in apt with open windows can listen and intervene if necessary.
I now consider this issue is closed.