I had the same question!!!!!!
To be 100% real with you, go as comforatble as can be! We didnt have any males in our training, but loose, lightweight pants or shorts would be ideal. You will not want to fuss with your clothes when you are having a tough enought time trying to learn everything being crammed into your head. I would also suggest a sleeveless form fitting thin shirt (if you feel comfortable enough) or one that wont slide all over the place. Bring atleast 3 outfits so you wont feel gross throughout the 3 days. Your nose will thank you 
LOL.
Just to share a laugh with you, when I went to training, I brought one of my favorite bras (If you dont care to read you dont have to) LOL . But, I prefer the ones with the straps that can be removed because I dont like when my straps show. So, we are going through the motions on the Sun Salutations, and, !!POP!! There goes my bra strap! I was mortified! So imagine my desperation while trying to fix myself, while still trying my best to keep up! (Our presenter was recording the class) But, I doubt you will have that worry
Good luck!
Kia Kaha!
<3 Tiffany