http://www.revscene.net/forums/450910-hong-kong.html
To answer your questions quickly:
No car necessary. MTR+buses can get you pretty much everywhere in HK.
What did you want to do/see there? There's something for everyone there depending on what you wanted to do/see. If you like to shop, are you looking for anything in particular?
I stayed in Tsim Sha Tsui (pretty central to everything). The Salisbury YMCA is a great cheap hotel. You'd have to book early though (either directly, or something like hotels.com). I booked flight and hotel separately.
And don't worry too much about language. As someone who didn't speak a lick of Canto or Mandarin, HK was a blast.