This is at D7 (number 43) on this map of the university (in pdf format).
Hotel Schwan, Mozartstrasse 24-26
Tel.: 0228-634108, Fax: 0228-651793
(Mozartstr. is the parallel road between
Herwarthstr. and Wittelsbacherring at D6 on the map)
a) Taxi
b) Bus from the bus station opposite the railway station:
Take bus 620, 624 or 625 (direction: Poppelsdorf / Ippendorf / Venusberg);
get off bus at "Poppelsdorfer Platz" (it is a 5-minute bus ride and
the stop is the one after "Am Botanischen Garten");
at Poppelsdorfer Platz walk to the traffic lights, then turn right into
Sternenburgstrasse, the hotel is a few meters away.
The airport bus ticket is valid for the ride to the hotel as well.
c) A pleasant walk (15-20 minutes), if you do not have too much luggage:
From the bus station, cross the railway lines using the underpass,
or leave the railway station at the Quantiusstrasse exit
(Westausgang). Then use the
map. The nicest way is along the Poppelsdorfer Allee,
Meckenheimer Allee and Clemens-August-Strasse, then left into
Sternenburgstrasse.
Links to other maps of Bonn may be found here.