Hi Kate,
I've worked pet friendly properties for a number of years, and have tried it all. For us, the reality is that no grass is going to survive near the exit of the building. When a dog has been inside all day/night and walks out the door, it is going to go straight for the first patch of grass it sees.
Cayenne deters some dogs, but you have to reapply it after every rain. Signs directing the owners to take the dogs elsewhere just serve as a convenient target for the pets to pee on! When reseeding, often the grass won't even sprout due to the acidic soil. Thorns and aromatic plants only deter a small number of dogs.
The only long-term success we've had is to install artificial turf, or use stone/mulch ground cover instead of grass.