The time for account approval can vary quite a bit, seemingly regardless of how it is paid for. Some accounts can be approved within minutes, while others can take days.
When I first signed up (paying by PayPal), my account was up and running within 10-15 minutes. However, a friend of mine signed up the next day (also paying by PayPal) and his account wasn't approved for 3 or so days.
About all I can suggest is to sit tight and wait for the approval email.
As far as I know, you have to specify any promo-code during the sign-up process. If you didn't do this then I think you are out of luck, sorry.
Also, I recall DreamHost changing things a while ago that removed the ability to use a promo-code if you were paying by a method other than credit card. I am not 100% sure this is still the case, but I suspect that it is.
Save [color=#CC0000][b]$50[/b][/color] on DreamHost hosting using promo code [color=#CC0000][b]SAVEMONEY[/b][/color] ( Click for promo code details )