Here is a quick summary of some of the areas in the city of San Diego. La Jolla and Scripps Ranch are upscale and wealthy. The nice middle class areas of town are Pacific Beach, Tierrasanta, Clairemont, University City, and Mira Mesa. Pacific Beach is a mixture of apartments with college students and young professionals, and single family homes. If you can afford it, it's one of the best places to live in the city. University City is near La Jolla and UCSD and is mostly upscale professionals. Clairemont is middle class single family homes and has a lot of military families living there. Mira Mesa has a large Asian population. Hillcrest is the center of the gay community. Mission Valley is young professionals and almost all condos and apartments. Ocean Beach is a lot of druggies, hippies, and beach bums. Mission Beach is the seasonal rental party animal types. Point Loma is a lot of retired military. The College Area is near San Diego State on the eastern edge of the city. Linda Vista is lower middle class and ethnically mixed.
http://www.sandiegoreader.com/news/neighborhoods/pacific-beach/
In general, the farther south you go (closer to the border), the lower the property values. IMO you want to live north of I-8 and west of I-15. There are also nice bedroom communities along the I-15 corridor, such as Poway, Ranch Penasquitos and Rancho Bernardo.
The North County Coastal area is one of the best places to live in the county. The beach cities of Del Mar, Encinitas, Solana Beach, Lucadia, Carlsbad, etc. are all great and many people do the daily commute on I-5. Also, The Coaster is the commuter rail service along the coast that takes you right downtown.