Great HQ for a San Diego experience
First, I live in San Diego and work in the Gaslamp.
Gaslamp is a great place for a lot of things, but Union Square, Times Square, Las Vegas Strip, it is not. The Gaslamp Quarter runs along Fifth Avenue from the Convention Center by the Bay up to Broadway St., about 13 blocks. In this area, you can find a multitude of restaraunts, clubs, furniture galleries, shops, multiple playhouses, and a movie theater. Horton Plaza, a large multi-level mall, is located adjacent to the Quarter. Gaslamp also hosts most of San Diego's historic buildings.
In the greater Downtown area, the San Diego Symphony has its home, there are more playhouses, the Embarcadero is a wonderful park/mall/tourist trap that actually does have ambiance and a number of tasty restaurants with awesome views of the Bay. Whale watching excursions leave from the piers at the foot of Broadway, as well.
Gaslamp is situated between Balboa Park (home of the Zoo, a number of museums, and an all around great park), the CBD, the Convention Center and Bay, and Petco Park (home of the Padres).
Gaslamp sepcifically (and Downtown in general) is a great place to stay on vacation, as there are numerous hotels. The hotels range from the vey luxurious US Grant to the ultra-modern Omni to the party-atmosphere Ivy to the multiple budget-friendly Motel 6 and Best Westerns. In addition to plentiful accomodations, it is centrally located in the City and County, and easily accessible to the Airport, the major freeways (I-5, SR-163, I-15, I-8), and major atractions such as Sea World, Mission Beach, Ocean Beach, Pacific Beach, etc. The main train station is located in Downtown, as is the cruise ship terminal.
Parking is only an issue if you aren't used to going to downtown areas of large cities. There is plenty of parking - if you are willing to pay. San Diegans in general are resistant to paying for parking even at meters, much less having to pay $1 an hour at a garage on a weekday evening.
An easy way to get around (besides your own two feet) are the pedi-cabs. The carriers know the town and can help you get places easily and recommend things you might like.
The Quarter can get rowdy in the evenings, but that is part of the allure for the younger set. If you wanted to drink in silence, you would go to a dive or your neighborhood TGI Fridays, right?
If you are travelling on a budget, there are a few hostels located in the Gaslamp, as well as a few more in the greater Dowtown area.
There are several events that Gaslamp and Downtown host annually, such as a very popular Mardi Gras festival and parade, the 5x5 block party (Cinco de Mayo), the prestigous San Diego Film Festival at the classy Pacific Theatres Gaslamp 15, the world-famous San Diego Comic-Con, a number of annual fund-raising marathons, the "Haunted Trail" at Balboa Park for Halloween, and many, many more.
In general, San Diego is a great place to visit (and live if you can afford it!).