I did mention in an earlier post what to wear (and not wear) in Bikram. Less is better. Here are a couple of outfits regularly seen in a Bikram class and some I wore that I liked and did not like. The down side of wearing shorts comes during the floor work. When pulling the knees into the chest, wrapping arms around the knees and grabbing elbows with opposite hands, the slippery-ness of the sweat makes it hard to grip your skin. A towel does come in handy and I used a large regular size bath towel over my mat and a smaller light weight, absorbent, fast drying hand size towel to wipe away the sweat. Very handy. I also used the smaller towel over my skin for grip in several poses.
SWEAT: The suggestion (from several instructors) is to NOT wipe away the sweat as your body has to work harder to cool itself down replacing the sweat you just wiped away. Wiping the sweat also clogs your pores, creating a breeding ground for acne. I did not experience either of these scenarios even though I DID wipe the sweat to keep it from dripping in my eyes. It stings.