Thanks for the replies so far - I was going on what Frommer's had to say on the driving situation re. both I-35 and the Austin area.

The Hill country suggestion sounds excellent and one I was already considering. As for Austin, the State Capitol and the Johnson Library are the two things I'm keen on seeing and, from what I can see on the maps, they are pretty close so I could probably even just stick the car in a parking lot for the day and cover the rest on foot.

Thanks - any further suggestions gratefully received.

David