Most tour agencies offering treks to Pinatubo are based in San Fernando and Angeles City. The Philippines generally has dry and rainy seasons, but the onset of El Nino a few years ago has left the weather more unpredictable. It's best to check forecasts daily. Visitors from other nations, including China, India, Pakistan and Taiwan, need visas. Best to check.
Shorts are preferable as there are many stream crossings.
A heavy load will really slow you down. Public sanitation is a problem in many rural areas. Drink only bottled, boiled or treated water. Guides with first-aid training are usually provided in a tour package. The plains, covered with gray ash that reflects sunlight, can make a warm day hotter.