Ron,
I fly into Liberia frequently, and I am not aware of any 'monger' spots in Liberia. There's a few local bars and cantina's within a few blocks of the city's major intersection, but you'd be trying to pick up non-working locals, and if your español skills are not up to par, forget it. There's a few working girls in Playas Del Coco, about 25 mins. South of the Liberia Airport, but you gotta search for them in the local bars. Either head South to Flamingo Beach (about 1hr. 15 mins) or stay in San Jose. Liberia is not known for the extracurricular activities.