Take bus 400 from the tachana merkazit (on Yaffo street). The ride to Bar Ilan is about 50 minutes. Ask the driver to drop you off at Bar Ilan University. The bus stops about 100 meters short of one of the entrance gates to the campus (note that the location of the stop has recently been changed and the bus no longer stops right next to the gate). Walk to the gate, enter the gate, and turn left. You will reach the mathematics building within five minutes.
The buildings on the Bar Ilan campus are numbered. The mathematics building is number 216. Use the entrance door near the corner of the building which is the furthest from the campus gate, for easiest access to the mathematics department.
The colloquium is sunday at noon, in room 201 (note that the room numbering system has been recently changed). It is on the top floor of the mathematics building. The current organiser is Prof. G. Soifer. The secretaries are on the middle floor, in office 103 (according to the new system).