Wearing a suit, coat and long sleeved shirts are definitely the way to go if you want to stand out from the crowd in Puerto Princesa. Being in the tropical country of the Philippines, and especially in Puerto Princesa where lush tropical forests and white sand beaches abound, the only real attire are light casual wear when touring the city proper and beach wear when relaxing on the beach.
During the rainy days from July to November, a few warm garments you can put on top of your lighter ones will help. This can also be used during cool and chilly nights when hiking up the mountainous areas around Puerto Princesa.
Always expect to rain or get wet in Puerto Princesa. Even though there are distinct seasons in a year, the common occurence of El Nino and La Nina can make weather patterns pretty unpredictable. A light jacket and an umbrella should do the trick.
For footwear, always bring flip flops or sandals and a pair of closed shoes such as running shoes when strolling through forested areas.
Aside from the above, insect repellant for mosquitoes is a definite must to ward of those pesky little insects.