The town of Tamarindo has two fun breaks: El Estero, a excellent rivermouth break where the Tamarindo Estuary hits the ocean and Pico Pequeno, a lava finger reef which can get perfect with a swell.
Midtide is best for both breaks. Go surfing any tide except dead low, its usually unsurfable on low tide.
Tamarindo's climate has two seasons, dry and rainy. The dry season, from November through April, is dry, hot and sunny. The humidity is very low and comfortable. The rainy season begins in late April or early May and continues through October.