February 6 search yields the following:
March 6 - 7 (IMA only dates) still showing hotel availability:
> Hampton Inn downtown: $219/night, couple blocks away
> Radisson downtown: $185/night, couple blocks away
> Wyndham Garden Inn Airport: $127/night
> LaQuinta Capitol: $109/night, couple blocks away
March 6 - 13 (iMA and SXSW Interactive) is harder to find, but rooms exist. Also suggest keep checking downtown, people booked early and end up not going, so rooms do pop up.
> Crestwood Suites Austin: $71/night, 14 miles northwest
> Holiday Inn Round Rock: $122/night, 20 miles north on I35
> Red Roof Inn Austin North: $61/night, 17 miles north on I35
> Lakeway Resort & Spa: $238/night, 23 miles west