Dear Michael, The Surinam Cockroach is typically found outdoors in warmer climates. You should consider using baits that can be placed in out the way places in the plant beds. These baits will normally control the population. Since it is a public space, you should use a licensed pesticide applicator that is properly licensed by the State of Illinois and carries the proper insurance. Be sure to ask for copies of those documents.
Sincerely, Richard