There's more to this little city than meets the eye.A kayaker on the San Marcos river.Credit: Visit San MarcosKey PointsThe spring-fed San Marcos River stays 72 degrees Fahrenheit year-round and is central to the city’s outdoor culture.San Marcos has a live music scene with deep local roots, historic venues, and laid-back bars with performances throughout the week.Beyond the outlet malls, the city has whimsical mermaid history, easy river access…