I'm going to expand on my previous comment.
1. Prostitution is legal in Costa Rica - pimping and pandering aren't. But that doesn't mean Costa Rica is a giant whore house (and those are actually illegal - the whole pimping and pandering thing). There's lots of places where you won't find
any.
2. Gringo-oriented* prostitution is not found everywhere in Costa Rica. The two main areas are central San Jose (the Gringo Gulch area**) and Jaco (predominately at the Cocal).
3. You can also find 'national-oriented' prostitutes (i.e., their market is Ticos) throughout the country in places like Guapiles. These maybe part-timers. The thread I linked talks about seeing girls on the street in Tamarindo. The source for info on these is
http://www.forodecostarica.com in the adult section but threads there about these off-the-beaten path places are as scarce on details as here. And forodecostarica is in Spanish. Idiomatic Tico Spanish and slang.
You can also look on
https://cr.skokka.com and wanucios for Guanacaste -
https://guanacaste.wanuncios.com/eroticos-profesionales-195.html but don't hold your breath as there aren't any on skokka and what's on wanuncios is gay.
4. There is little first-hand knowledge here about working girls in places like Tamarindo because most of us don't go looking for working girls in places like Tamarindo. See 2 above. Tamairindo is a surf-and-beach tourist area.
5. If someone goes into a club in Tamarindo and assumes every girl is a whore that person is liable to not enjoy their evening.
6. You can always ask a sleazy cabby and he might set you up - and maybe you wn't get robbed and / or murdered.
7. Working girls in Costa Rica don't have 'health cards' - they may pay their national health insurance and have an insurance card, but it isn't a 'health card'.
8, The best way to find P4P in places like Tamarindo (or San Isidro del General or wherever) - IMHO - is (a) Badoo and (b) Tinder; but you need to play a long game (start a couple of weeks out). It's a risk because they might be fat or whatever.
If you have time, you can find girls that need rent money or food money or whatever money. But it takes time.
The Hotel del Ray or the Cocal or the SL or any of the salas (MPs) is point, click, discuss / negotiate and go.
* Gringo in the sense means foreigners.
** The Gulch as in the HdR, the SL, HLH, the strip clubs like Alcazar, and all the various salas (MPs) like Z2, Relax and Monicas even if they aren't in the Gulch per se.