The workshop will be with the POPL conference. Below is the hotel information from POPL:
The conference will be held at the Sheraton Society Hill Hotel in Philadelphia's historic district. To make reservations at the special conference rate of $139/night, go to http://www.starwoodmeeting.com/Book/POPL2012. Alternately, call the hotel directly at +1-215-238-6000 and mention the group ACM/POPL 2012.
We realize that you may want to consider other hotels. Before you decide, please read why you should try to stay at the conference hotel.
To be eligible for the special conference rate, bookings must be made by December 24, 2011. However, as the conference rate applies only to a limited number of rooms, attendees are encouraged to make their hotel reservations at the earliest opportunity.