San Diego holds a rather interesting and diverse music scene.It's fragmented for the most part; many small oases in the desert are there gatherings at specific locations that predicate the style. Want Blues? Go to the Gaslamp downtown or the Kraken in Cardiff for the North County crowd. If it's Latin music you crave, check out Croce's in the Gaslamp or venues in the North and South County venues.
For original music be sure to check out LeStat's Coffeehouse, Brick by Brick, Humphrey's (on selected nights), and oftentimes the Casinos will put on original evenings.