Unfortunately the trolley system in Austin - the 50 cent 'Dillos (short for armadillos) that ran up and down Congress and up and down 5th and 6th Street have been suspended due to budget cuts as of October 2.
Visitors should take this into consideration as they consider hotels. It is very easy to walk to many of the most popular attractions/music/restaurants if you're staying in the downtown area. With the fall weather arriving the heat will not be such a factor.
It is also easy to catch a cab in central Austin.
Hope this info helps in deciding on lodging.