Jaco #1, Tamarindo #2, Flamingo ?3
As far as sheer volume of women and thus more flexable pricing and options, Jaco is the best beach town I have been to. It does seem that the trade off is the seedy element and overdevelopment. I went to Tamarindo recently and hooked up with a Tica for free for 6 days. Turns out she was a drunk and was just happy to have an open bar tab every day. Did not see too many opportunities for mongering but they were there. Definetly a nicer town, though, again it seems you have to trade off the natural beauty of CR for the overdeveloped areas if you want to find the willing Ticas.
Older posts have suggested Playa Flamingo as a decent mongering spot, and have said Manuel Antonio is poor at present. I am going out next week and will hopefully hit a few of the beach towns including Flamingo.