The Gaslamp Quarter was exactly the place I was going to suggest. It's our historic downtown quarter and has a lot of restaurants and clubs, is near to major hotels, and the San Diego Trolley.
http://www.gaslamp.org/articles/arti...fter_dark.html
I'm not a nightclub person; so, unfortunately I can't really recommend a place. The only place I've been is Deco's at night when it's a club. My friend just celebrated a birthday at the rooftop bar at the Ivy Hotel.
The only other place I might suggest is Pacific Beach...but it's kind of hit and miss sometimes and not nearly as much of a "destination" as the Gaslamp Quarter.
http://en.wikipedia.org/wiki/Pacific...go,_California
"Bars and Nightlife
Pacific Beach is one of the main centers of nightlife in San Diego. Garnet Avenue between Ingraham Street and Mission Blvd. is the main area where bars and restaurants are located. Pacific Beach tends to cater towards a younger, more college & post college oriented crowd compared to downtown San Diego's Gaslamp District. Dress codes are generally less strict if they are enforced at all.
Some of the larger and more popular bars in Pacific Beach include Cabo Cantina, Pacific Beach Bar & Grill, Moondoggies, Tavern At The Beach, Nick's at the Beach, and Typhoon Saloon. There are also a good selection of medium sized bars and a few smaller local places such as PB Pub, Thrusters, Cass St Bar & Grill, and The Silver Fox. Lahaina Beach House, located on the Boardwalk at Reed Street, and Open Bar (on Mission Blvd.) are popular on sunny days."
Also, I've heard of people going to the Wave House in Mission Beach, which is just south of Pacific Beach.
http://www.wavehouse.com/home.asp MB can be a little awkward around Belmont Park (by the arcade and roller coaster) in the evenings as people like to go cruising there. Gaslamp and PB are better choices.
Good luck! I hope you all enjoy San Diego!
.....Kelly