1st Dilemma/Problem!

Ok I have encountered my first road block and I am confused and looking for help. Might get on to German Consulate here in Cork if I can't figure it out or if people can't help!

To open a Bank Account I have to register my address, is there a point if I'm going for 6 months? Especially as a live-in au pair?

I know if I stay longer and get a job and apartment I will have to, but what about my first six months?

Ideas anyone?