I’ve recommended Yum Cha in the countryside. How about trying Yum Cha in the New Territories? I had Dim Sum in the Yuen Long Family Restaurant (元朗人家) in Yuen Long weeks ago and it was a delightful experience. The dim sum and dishes were good and the price was unbelievably low, compared to the restaurants in the city. We had six adults and two kids for Yum Cha and the bill was only about HK$350. My favorite dim sum/dishes are steamed rice roll (腸粉), steamed fish balls(蒸鯪魚球) and fried rice (炒飯).
There are two Yuen Long Family Restaurants near the Yuen Long MTR station. The one I went to is a branch, at Hung Wan Centre, No. 19 Fung Kum Street. (updated on 20 Aug 2011: this branch has been closed.) The other has a lmuch onger history, at Transport Plaza, 2-6 Fung Cheung Road, and is also more popular as it is closer to the centre of Yuen Long.
Yuen Long these days still retains some characteristics and tradition of it old days as a market town. There are few luxury stores and more local shops here. You should come here to see more of Hong Kong.