I'll have to check out goodwater loop! I've never heard of that. I'm in north Austin and head to walnut creek pretty often. It's really nice, especially if you can go on the weekdays to avoid the crowd.
Also, love Mckinney falls state park. It can be crowded but I've found that once you cross the river the trails on the north side of the park are generally empty. Also nice to jump in the water after a long hike 🙂