It's best to check forecasts daily. No visa is required for citizens of many countries, including the United States, with a stay of up to 21 days provided they have tickets to leave. Visitors from other nations, including China, India, Pakistan and Taiwan, need visas. Best to check. Light casual clothes are recommended for the trek due to hot, humid weather around Pinatubo.
Shorts are preferable as there are many stream crossings.
A heavy load will really slow you down. Filipino is the national language, although English is widely used, especially in business and government. 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.