You can refer to the sticky thread about Williamson county.
http://www.eccie.net/showthread.php?t=654993
You could also do a search in coed for "good incall location " and that will probably produce several threads that previous traveling providers have asked. Here are a few links but you can find more if you like.
http://www.eccie.net/showthread.php?...=good+location
http://www.eccie.net/showthread.php?...=good+location
http://www.eccie.net/showthread.php?...=good+location
I don't think downtown is that great of an option, it's expensive and traffic and parking can be hassles.
Up North Austin I would recommend the Arboretum area or the Domain area, they are nice locations.
The Vagina triangle, I35 , 290 , 183 area is quite popular with traveling providers but some locations are a bit sketchy.
Also you might check a few dates when booking hotels. There are frequent events in Austin that can greatly effect hotel rates week to week.
Best of luck to you.