One thing to remember on the buses is that if you pay trip by trip in cash no change is given, so you will need to keep a few coins. I would say get the Octopus - you will probably save money (provided you remember to exchange it back at the airport to get the HK$50 deposit back) because otherwise you will end up overpaying for some busrides through lack of change. It also saves a lot of time buying tickets at the MTR stations.
To go to Stanley I would always take the plain #6 since it is the only one which goes over the top of the hill rather than through the tunnel (6A, 6X, 260). The advantage of getting it from the start of the line at Exchange Square is that you can dash on first and get the front seat upstairs which is definitely the best place for the view.
If you do get it from Pacific Place (where the Conrad is) you simply need to cross over Queensway (the big road out the front of the Mall) - the stops for all the Stanley buses are on the road itself, not in the undercover area (it will be obvious what I mean when you are there).
The bus drivers do generally have some basic English, but Stanley Market is pretty obviously where everyone gets off. Some of the #6... services terminate at the market, and some go on only one or two stops - Stanley is on a peninsula, so it isn't possible to go much further - the Prison is the only thing further out!
The Citybus site (above) is pretty good.
[This message has been edited by christep (edited 10-14-2002).]