Been there 6 times in the past year on business mostly. It depends what you like really - I agree with the earlier post, TripAdvisor "Things to Do" is a great place to start planning.
The city itself is quite walkable - November will be better for that - right now it's way too hot - and a few interesting landmarks/buildings around, including the State Capitol. There are loads of bars and music venues particularly around Sixth Street - but depends whether that's your thing (I went there once and that was enough for me
)
Different people will give you different answers on the "best" place for BBQ, but you really can't go wrong, it's all great in my opinion, especially if you order the 'moist brisket'! There are loads of other great places to eat though including food trucks, and lots of amazing small local breweries within easy driving distance.
You'll get more value for money if you stay outside the city for at least part of your trip and rent a car to travel out to surrounding areas. There are some nice scenic views and places to stay around Lake Travis where you can take out day-rental boats, kayaks, paddle boards etc.
If you do travel further afield to other cities, it's fairly easy to drive despite some long distances - big straight roads and the gas prices are some of the cheapest in the country.
The flights to/from Austin so far have typically not been full aside from when special events are on, which means it's fairly easy to end up with some extra space on your flight, with Fridays being the busiest day from what I've seen.