Right now during the winter months sunfish are usually not very active.
I know the areas Cypress Bend Park and Landa Park very well and the sunfish bite is normally slow during this time of year.
Landa Park being a warm water river(Comal River), you may have some luck there. The Comal will start producing some super nice Redbreast during March and April. Also the Blanco River is not that far away and the sunfish bite will be getting active as well. Good luck and keep us posted on how you do.
Side Note: As for the Rio's. The Comal is loaded with them. Late March through October the Rios will be active. The Guadalupe also has a good population of Rios.