Whitty:
The date the enrollment deposit is due was not listed on my acceptance letter, either. I couldn't find the information on the SSW's site or on the Graduate School's site, so I e-mailed Metta Prietto in the SSW office. She replied saying the following:
The due date for paying the $250 deposit is actually the 15th of April (in two days). Paying the deposit will not automatically kick any information your way, but I just spoke with Sharon Thomas, our Director of Admissions, and she said that in mid-May you can expect a Welcome packet with more information for incoming students. Financial Aid decisions should also be made within the next few weeks and you will be hearing back from us, whether or not we were able to grant you funding.
This implies that the deposit is due for everyone tomorrow, regardless of a funding decision. Maybe they'll be flexible because we haven't yet been notified of possible funding, but I went ahead and paid it yesterday to secure my place in the class.
Good luck in your decision!