Luckily, I live on a quiet cup-de-sac and have a side street that is also dead-end, so we have a 4-block radius that we can walk which would total 8 blocks to and from. We also have a park at the corner where the tennis and basketball courts are that has a lot of grass. The thing is you do NOT want to spook your kitty because then it becomes a fight against the leash and harness and if the harness is not attached securely, your cat will get away. There are other ways for a cat to enjoy the outdoors.
There are portable enclosures that can be put out into the yard and folded back up when the cat is not using it. There a more permanent enclosures -- some merely extending wiring outside a window and allowing the cat a perch that will give them some fresh air. Or building an enclosure in the yard. While most owners want to see their cats have some fresh air -- once the cats whiff it, then it becomes their requirement to enjoy it. There are pet buggies where you can wheel your cat around (stroller -- baby) and the cat is safe inside. Doesn't get the exercise (but at least you do), but it does get the cat some fresh air.
The key is to make sure your kitty stays safe. It's up to you whether you want to risk the outdoors, even with a harness and leash. It can be a great time to bond with your kitty. If you feel your area is too busy, you can transport your cat to a more open area or park, however, if the cat gets away from you -- the cat is not going to know where "home" is. A nice quiet road would be the best when you are first starting your walks. Raiden gets spooked if I accidentally kick a rock.
Still recuperating from my fall, but doing better. I'm just not walking as fast as Raiden these days.