Sri Ramakrishna College of Arts and Science, which used to be called SNR Sons College, is a well-known college in Coimbatore. It started back in 1987, making it one of the older colleges around. It's an autonomous institution with a high A+ Grade from NAAC. The college is coeducational and is conveniently located in the city center. It also has affordable fees and a strong network of former students.
PSG College of Arts and Science is a great choice. Then there's Krishna College of Arts and Science, which is also well-regarded. Dr. N.G.P. College of Arts and Science is another good option. You might also consider Karpagam College of Arts and Science. Lastly, Nehru College of Arts and Science is worth checking out.