Beijing
Pleco is excellent, if you also need a small electronic dictionary to carry, try the 文曲星 pc1000c, it's not as fast or useful as Pleco, but it displays pinyin, has pinyin search, radical search and stroke search. I'm sure book stores all over town carry them, but I know the large bookstore at the ChangAn end of WangFuJing has them for around 270¥.