Walking in HKG is brutal in the summer. You're right on the avenue of the stars, so you can walk to the star ferry terminal along the harbor. If you do that at night, you also get the view of the island, which even beats Hoboken for the best view on Earth. It's not a long walk, but even at night you'll be covered in sweat when you're done.

The Jade market and bird street require an MTR ride to Mong Kok, but that's not too far.