What a fun trip! I’ve never been to SXSW so my style guess is as good as yours. Still, as with any short vacation, pack light, easy, and iron-free. A few cute dresses that you can wear day to night, a slouchy knit sweater to layer, a skinny jean, a button-down for day and slinky blouse for evening. One heel, one flat, one fantastic bag to pull it all together.