I love Austin and would jump at the chance to live there, but having spent all of my 28 years in North Texas, I can vouch for the disgusting heat and humidity. It's October and I'm still sweating hard on the ride home. The temps are nice, but humidty is usually a minimum of 30 something percent, usuallly 70-80% in the mornings. Last couple of weeks it was 50 in the mornings and well into the 80's in the afternoon. My route is 10 miles one way, so I shower regardless, but even a 2 mile ride on an average summer day would leave you drenched.

In terms of biker friendliness and enough of a downtown to get away without a car, I'd say go for it, but it really depends on if you can stand the heat pretty much. Some live with it (me) but others couldn't be paid enough to live in it.