I believe Dreamhost support is located in the US. I could be mistaken. The worst day to contact support for almost any US company is on a Sunday/Monday morning. It is currently 2-3 in the morning as you write your question.
I would imagine that you should get a response sometime within the next 24 hours, however in the future, keep in mind that most US companies don't have a Sunday support. Some don't even offer support over the entire Saturday-Sunday weekend, as the employees are having their weekend time off.
If you're really in a bind, I believe you can call support regarding any "urgent" or "emergency" methods of contact, which may cost an additional amount.