Where to exit
Take the train to Cologne main station (Köln HBF). There are several cheap rates offered by Die Bahn: e.g. the Wochenendticket (for those of you who would like to arrive on saturday and miss half of the party), the Mitfahrerrabatt (drive in groups up to five persons, where everyone except the first person will pay half of the regular price, only) or even cheaper prices for larger groups. If you're planning to come via train from abroad, simply check the homepage of your national train company.
How to get to the partyplace
Exit the station through its main entrance, leading towards the cologne cathedral (kölner dom) and the city center. You should see the cathedral to the left (yes. take a second to enjoy the view) and rather ugly stairs leading to the plateau.
As you can see the bus stop is right next to the rightmost stairs on the other side of the road.
At the bus stop wait for the next 132 direction Meschenich. Tickets are available inside the bus (short distance ticket called "K" at 1,25 €) -- have coins handy.
After around 20 minutes the bus stops at "Alteburger Wall", leave the bus and cross the street.
You are now on the Alteburger Wall, which turns into Oberländer Wall at the next crossing. At Oberländer Wall you will pass a kindergarten and right after that is the Friedenspark, as you can see on the map. When the street turns left you will find the location to the right. You are there!