The best times to go to Costa Rica are January or July and August. The four main things visitors consider when planning a vacation are costs, crowds, climate and convenience. Not surprisingly the most convenient times for travel (Christmas, New Years and Easter/Spring Break) are also the most crowded and most expensive.
As you can see on the chart the ideal dates for a trip to Costa Rica are shifted a bit away from when the majority of travelers have vacation time. The crowds are cut in half a few days after January 1, the dry season provides perfect sunny beach weather and prices are much lower than the peak season.
There are even fewer visitors in July and August but there is a bit more rain in the forecast. There’s even more rain in May and June and most people are stuck at work so it’s easier and cheaper to get reservations at the top rated accomodations.
If you’re on a budget the least popular months of September through early December are the cheapest but also the wettest (unless you head to the Caribbean side for the secret dry season).