I've lived in Austin for 16 years and I've never heard of this place. It was terrific. There was no one there. We saw a few people on the river, but no one in the park. It could have been because we got there at 9:00 on a Sunday and the park does not open until noon for cars. We just opened the gate and walked in. The falls was not a falls because there was no water but the hike was terrific.
There is also a great area for picnics. This is a spectacular park in the middle of town. I highly recommend it and I will be back.