Howdy, and Welcome!
Some fishing for rainbows can be found on the Canyon Lake Tailrace down near Austin. These trout are stocked each year by the Texas Parks and Wildlife Dept., but the water coming out of the lake is cool enough for their survival. Access to the river is a bit restricted, but if you go to the website for the Guadelupe chapter of Trout Unlimited, you can find some info. Also try the Parks and Wildlife Department website. That will give you the stocking schedule.