Hey Swati ! I was in Coorg last August. It did rain a couple of times then. But October and Nobember is a great time to Visit Coorg. It is a beautiful place to relax as well as a place for trekking enthusiasts. As far as attires are concerned you can carry some light jackets. Since it is a hill station it may get a bit chilly towards the evening. You won't find people wearing very fancy stuff there. I was pretty comfortable wearing simple western clothes like a jeans and a tee as well as wearing Kurta and leggings. Avoid wearing heels and wear comfortable sport shoes or sandals as you may have to hike a little to check out the waterfalls ! Have a great trip ! :)