This is the Gaya Street I've been talking so much about. It's a narrow street lined with eateries, shops, budget hostels, one boutique hotel (from RM100), one internet cafe and one very-known Chinese restaurant whose speciality is the body parts (e.g. liver, intestines) of a certain animal known for its obesity.
(business opens only in the evening; name is Yu Kee)
I took a city bus but had to get off somewhere nearby, but it's only a 5-minute walk to Gaya Street.
From Gaya Street the waterfront is only 5 minutes away, the Jesselton Jetty 10 minutes, shopping malls 5 to 15 minutes.
To Signal Hill, take a shortcut beside the police station. A short staircase leads to the top of the hill, passing by the Atkinson Clock Tower. I chanced upon this shortcut on the way down. I had a panoramic view of the whole city of Kota Kinabalu and the ocean from the top of Signal Hill. Worth the effort.