This sign was in season 1 episode 2 of White Dragon which takes place in Hong Kong. I was hoping someone here might be able to shed some light on what it says. Thank you!
It is '春夏秋冬行好运' written in traditional Chinese ('春夏秋冬行好運').
In this sentence, '春夏秋冬' means spring, summer, autumn and winter by order, '行好運' means 'good luck'.
Put them all together, it says 'good luck for whole year'.
Just in case you're interested, this is a couplet, it usually comes in pairs. The second line is ‘东南西北遇贵人’, which means wherever you go, you'll always meet nice people.