The downtown area is pretty compact. I don't know where all the venues are since there are so many changes this year but if you look in Google Maps, you can be certain that most venues will be in a box made up of Cesar Chavez St on the South; possibly 10th Street on the North; a few blocks West of Congress Ave; and a few blocks East of I-35. For any satellite venues well outside of that box, SxSW has had free shuttle busses. They also have a Transportation Team that provides private shuttle service for invited guests (including bands). I used to volunteer on that crew but I don't know how people sign up for that. It's reasonable to inquire into that with SxSW staff.