End March & beginning October are the best time to be in HK. There'll be rain mid April onwards. July/August is damned freaking hot (with constant sprinkle of aircon water). December is good if you want to experience typhoon weather.

Queue wise - HK is a crowded city with lots of visitors from just about everywhere. Used to be even worse 3-4 years ago when the "buyers" from Mainland crosses over every single day. You are expected to queue up for almost everything including lunch and dinner.

Oh btw, get sufficient HKD there (exchange it here) cos the MYR/HKD rates at MCs there are atrocious. They will dip as low as 1.4/1.5