Are you pets used to an urban environment? Will they only to the bathroom on grass? Unless you get housing with a yard/garden, I don't think there are many areas for a dog to go to the bathroom on the grass. I know this was a problem for some pet owners who moved their pets to NYC and seems as though it could be a problem here. Our dog is coming to HK next month from NYC as we only just arrived here.
Our decision factors in bringing him here were:
1) how long do we plan to stay - for us, at least 2 years - this was long enough in our minds to justify flying the dog here.
2) medical care - for us, we weren't worried about general vet care as there are lots of trained vets all over HK but our dog has a special eye condition that is hereditary so he sees a vet opthalmalogist to monitor the condition. In HK, there is no certified vet opth but I have emailed with a vet in HK who has been trained in eye so I will have him monitor his eyes and work with a vet opth back in the States to decide if the dog needs to change his meds.
I have seen even big dogs get in taxis in Happy Valley and the Midlevels so that shouldn't be a problem. But if you live in an area where you can walk to the vet, it shouldn't be a problem.
Dogs get walked on the sidewalks here in Happy Valley, they run at the dog run, and some owners take their dogs on trails.
I have been watching the whole dog bathroom situation so we are prepared when our dog arrives next month. Dogs pee on the sidewalk, curb or in a designated sandbox around the city and it's customary to bring along a bottle of water and wash it away. Dogs also poop in these same areas and people sometimes slide newspaper under the dogs behind so the it doesn't get on the sidewalk. There are special orange bins for the dog poop. I've also spoken with some dog owners/walkers who bring the poop home and flush it down the toilet - I've never done that before

.
Hope this helps.