The street market on Jalan Petaling is open every day from 10am until around 11pm in the evening. Most stalls sell pretty much the same items so it keeps repeating after a while. That means you have the chance to haggle down the prices quite a bit because of competition (up to 70% if you are talented in negotiating). Most common items on sale are - almost entirely pirated versions of - branded watches, handbags, t-shirts, shoes, belts and DVDs.
There are also a few good places to get Chinese food in the area.
Chinatown and the surrounding area is very lively, especially Petaling Street itself with the narrow space between the stalls can be overcrowded, during the day until about 11pm when the street market closest. After that the area turns quiet.
Chinatown is centrally located closed to the old colonial centre around Merdeka Square. From Bukit Bintang you can walk here in about 15min or take the Monorail to Maharajalela station which is around the corner of the southern end Petaling Street. If you are coming from KL Sentral or KLCC, you can take the LRT and get off at Pasar Seni. The Pasar Seni station is just to the west of Chinatown.
street market near Petaling Street selling fake designer items like on this picture handbags and wallets
The Kuan Yin Temple just next to the Maharajalela Monorail station marks the southern beginning of Chinatown
a traditional 5-foot-way of a Chinese shophouse in the southern part of Petaling Street (in the distance you can see the gate to the street market)
Guan Di Temple on Jalan Tun HS Lee
Reggae Bar and the western entrance to the street market on Jalan Tun HS Lee