I've worked in the area but never tried to monger there. Liberia is about the last place I'd go for a vacation or PFP. Your best bet for quantity and quality will be to head to San Jose or Jaco. But if that's your plan why not just go directly to SJO?
You might revisit CRT, and also
www.internationalsexguide.info, and do a search on beach towns that are close to Liberia. That's where you'd be staying anyway. There might be something in Tamarindo.