San Antonio – Texas Highway 16 is the longest road in Texas – that starts and ends within the State. Head out of San Antonio to the north and enjoy the scenery, and once you reach Bandera, if nothing else see the “Chicken Caddy”. You will not miss it. There is plenty to do in Bandera, but I recommend just riding (or drive if you must) north at least to Llano.
Along the way – Medina and parks along the Medina River; steep switchback roads on the way to Kerrville; find some great food and refreshment in Fredericksburg, see the Willow City Loop, a short detour to Enchanted Rock on FM 965, and on into Llano.
My guess is that you will return by the same route to San Antonio, and maybe stop to end the day at Floore’s Country Store in Helotes. You never know who might be playing that night.