I really don't know how helpful my advice is, but here goes!
Hmm... well with a salary of 10,000 HKD (a month I am assuming?), I honestly don't think you can really get much. Why don't you try a furnished apartment? I think for your situation it may be the best bet.
Food is pretty cheap, I thinnk you can probably do about $400 a week if you ate kind of average. Entertainment-wise, I'm not really sure, as I kind of blew all of my money on shopping

There's quite a bit of stuff to see and do (and buy), though I feel like the city itself is enough to keep you entertained.
And EVERYWHERE is pretty much close to a MTR station, so no worries about that. Good locations to check out: North Point, Causeway Bay, Central, Sheung Wan.
On a random note - how did you manage to score such a great internship?