Do I need malaria pills for Costa Rica?

For most tourist itineraries, no, and for some specific regions, yes. The CDC recommends that travelers going to certain areas of Costa Rica take prescription medicine to prevent malaria, which is very different from a blanket countrywide rule: the risk concentrates in specific lowland and border zones, while the central valley, most Pacific beach towns, Monteverde, and the usual tourist circuit sit outside it. So the answer comes from your route, not your country. Two things follow. First, get a proper travel-health consult, because the decision is region-by-region and your GP or a travel clinic can map your exact itinerary against the current risk zones and current outbreaks; the CDC's Costa Rica page, for example, currently carries a chikungunya travel health notice, another mosquito-borne disease, which changes the prevention advice toward bite protection even where malaria pills are not needed. Second, whatever the malaria answer is, mosquito defense is universal there: DEET or picaridin repellent, long sleeves at dawn and dusk, and air conditioning or nets at night, since dengue and chikungunya have no tourist vaccine plan for most people. If you are prescribed pills, start before the trip and finish the full course after you return.