Going on the Dream for Baltic 12 day. Planning to open an onboard account using cash. Does anyone know when you can open the account and is there a minimum amount that they require per person when you want to open an account in cash? I would think that they would return any money left in your account in cash as well in USD, right? Thanks for the info.

Yes, you can use cash to open your onboard account and money that is left in your account will be returned to you in cash at the end of thecruise. I am not sure what NCL's minimum cash amount is at this time, but be aware that the $10 per day per guest gratuities are automatically charged to your onboard account so allow for that cost.
Nancy