!!! IMPORTANT REMARK !!!
If you look on the map of the public transportation network it appears that a different route via 'Marienplatz' would be easier. Indeed, usually that would be (under normal circumstances) the preferred route, except that there is now construction work ongoing during the weekends.
The simplest way to reach the IPP from the airport is to take the public transportation line S8 up to the station 'Ostbahnhof'. Change there to the subway U5, direction 'Laimer Platz' up to the station 'Odeonsplatz' and change there to the subway U6 direction 'Garching-Forschungszentrum'. Leave the U6 depending on whether you have to go to your hotel first (e.g. Garching) or whether you want to come to the IPP directly (final station).
Please note: Some of the U6-trains do not go all the way to Garching and stop already in 'Freimann' or 'Fröttmanning'. In this case just take the next train.
Expected duration: 1h 19 minutes.