Luggage and bags:
If you're insane enough to go in the summer (I don't recommend it), bring the lightest clothes possible and a ton of sunblock. You literally get soaked when you walk out of your hotel room at night, that's how humid it is!
Clothing/Shoes/Weather Gear: Comfortable shoes. You will walk a lot.
Toiletries and Medical Supplies: SUNBLOCK!
Photo Equipment: As you can see, black and white film is practically a requirement here.