The weather is warm throughout the year, but the altitude keeps the temperatures from getting too high. Spring-like is the best way to describe the climate which makes it perfect for all the walking you will be doing.
The rainy season runs from April until November. During these months can expect a heavy downpour a few days per week. You can usually rely on the timing to stay constant. Expect rain during the window between midday and 3pm.
The weather gets a bit cooler during November to January, especially at night. The temperatures can fall into the 40s when the sun goes down. During the day you can still expect temperatures in the high 60s and low 70s.
The best weather is from February to June. This is the dry season and the weather gets up into the high 80s most days.