In short – please plan to choose and reserve your favorite hotel for this event from among the many hotels in Philadelphia. The organizers of the Workshop will not make a group commitment for a room block. (Advice: make advance and cancellable reservations to retain your flexibility.)
To explain: in our experience when we made a financial commitment to a recommended hotel with a set rate we often could not deliver the reservations because some folks had company-mandated hotels, others had personal preferences or even could get a better rate through their companies or due to the quirks of hotel pricing practices. All are perfectly understandable choices and reasons; however, this nevertheless leaves the organizers with financial penalties. This is the reason for not committing to a room block..
The hotels closest to the campus are the Hilton Inn at Penn and Sheraton University City.
Check also the Homewood Suites by Hilton.