You can get all directions to the institutes of the University of Bonn (PDF, german only) on the homepage of the University. The Physikalisches Institut, the Helmholtz-Institut für Strahlen- und Kernphysik and all conference sites are located on the Campus Poppelsdorf.
The entrance of the Geographisches Institut where plenary sessions take place and where the conference office is located is indicated by a blinking blue triangle on the maps of the General-Anzeiger Bonn.

Directions by car

From all directions - except from South-West:
If you are coming from the Frankfurt direction, follow the A3 up to the "Autobahnkreuz Bonn/Siegburg", then take the A560 until you get to the "Autobahndreieck St. Augustin", change to the A59 and follow it to the "Autobahndreieck Bonn-Beuel", and finally take the A565 to Bonn.
The same applies if you come from the Cologne-Bonn-Airport (via A59), then as above, or from the east of Cologne (via A59 or via A3, and A560), then as above. Direction Bonn is always indicated on these motorways.
If you are coming from the Cologne (west) direction, take the A555 until the "Autobahnkreuz Bonn-Nord" and then the A565 towards Koblenz.
From South-West:
From the Koblenz direction, take the A61 to the "Autobahnkreuz Meckenheim" and switch to the A565 towards Bonn.
All southbound (eastbound resp.) arrivals via A565
You leave the motorway at the Bonn-Poppelsdorf exit (as the conference site is in Poppelsdorf). This exit makes you automatically pass under the motorway from which you came (resp. leads you directly to the two track road), and you arrive at a two track road; this road first passes under a block. At the first traffic light go right, at the next one right again, and at the third one right again (so as to acomplish a 270 degree rotation). You are almost there. After the fourth street on the left (Nussallee), you can see a large yellow-brown building on your left with a statue of Kékulé in front. This is the Geographisches Institut, where the conference desk is located.
For directions to the Geographisches Institut also see this

Approach by Public Transport and by foot

Arriving at the ICE station Siegburg:
Down the stairs from the ICE platform to the Stadtbahn (to the right side) and enter Stadtbahn No 66 ("Telekom-Express") direction Bonn. Get out at "Bonn-Hauptbahnhof" and follow the description below.
Arriving at Bonn railway station:
Leave the main station by one of the west exits to the Quantiusstrasse and turn to right. At the next corner move left into the Meckenheimer Allee. Follow this street some 700 meters until you see on the right the Geographisches Institut, a large yellow-brown building with a statue of Kékulé in front, where the conference desk is located. The walking distance between the main station and the conference site is about 15 minutes.
Timetable information for all local public transport connections can be found here.

Map of the conference site

FB 19 conference site (click to enlarge)
(click for a larger image)