San Diego County is the southwestern-most region of Southern California. It encompasses the city of San Diego and its large metropolitan area, which includes many smaller cities and communities. San Diego County lies along the U.S.-Mexican border, across from the Mexican city of Tijuana.
San Diego County covers a very large area (4,526 square miles, to be exact) with incredibly varied topography. The western half of the county is mostly urbanized, and includes the city of San Diego and its many suburbs to the south, east, and north. The climate of the western half is more moderate, due to its proximity to the ocean, giving San Diego its signature weather. The eastern half is mostly uninhabited or rural, contains snow-capped mountains, forests, and barren desert, and is prone to more extreme weather.
Like much of California, English and Spanish are the dominant languages in San Diego County. Typically, most businesses have at least a few employees that are bilingual in English and Spanish, and some people will be bilingual in English and Tagalog (mostly spoken by San Diego's large Filipino population). It is also common to see store signs printed in both English and Spanish, especially in neighborhoods with large Hispanic populations.
There are two commercial airports in San Diego County: San Diego International Airport (IATA: SAN) is by far the major one, served by many airlines offering flights from cities around the country and some international flights to Mexico and Canada. McClellan-Palomar Airport (IATA: CLD) in Carlsbad serves a couple of commuter airlines providing service from Los Angeles and Phoenix.
Amtrak's frequent Pacific Surfliner San Luis Obisbo-Los Angeles-San Diego route serves San Diego County with four stops: one in Oceanside, one in Solana Beach, one at the southern end of the line at Union Station in Downtown San Diego, and a secondary station in Old Town San Diego which is served on weekends.
Three major interstate roadways, I-5, I-8, and I-15, lead into San Diego County. I-5 runs from the north along the coast, I-8 comes in from the east through the desert, and I-15 leads in to San Diego from the northeast.
In the western half of the region, a complex system of interstate highways and major roads connect the cities and neighborhoods of that half of the region. In the more rural Inland region, only I-8 and a small network of state and county roads run across the area.
The COASTER commuter rail system runs along the coast of San Diego County north of Downtown San Diego, linking together most of the coastal cities and towns of North San Diego County with Old Town and Downtown San Diego. Amtrak's Pacific Surfliner runs this same route, stopping in Oceanside, Solana Beach, and San Diego, but is less practical for getting around the county than the COASTER due to its high price.
In North County, the SPRINTER rail line runs east-west between Oceanside and Escondido. In San Diego, the San Diego Trolley light rail system links several cities east and south of San Diego to the metropolitan center, running east through La Mesa and El Cajon to Santee and south through Chula Vista to the USA-Mexico border.
The Metropolitan Transit System (MTS) and the North County Transit District (NCTD) operate public transit bus services in San Diego County. MTS serves San Diego and many of the surrounding cities, while NCTD serves North County. Service in the Inland region is pretty scarce.
Listed here are just the major sights to experience in the region. For more details, see specific city articles.
Balboa Park - A massive and utterly gorgeous urban park with gardens, Neo-classical Spanish architecture, and intriguing museums, along with the famous and expansive San Diego Zoo.
Sea World San Diego – Massive aquatic park with shows, displays and enclosures featuring sea animals. See the Mission Beach article.
La Jolla – A lovely coastal community of San Diego with scenic coves, beaches and ocean cliffs to explore, as well as museums, an aquarium, and the University of California, San Diego campus.
Cabrillo National Monument – Commemorating the landing of Juan Rodriguez Cabrillo's expedition for Spain of California in 1542, this park at the tip of Point Loma offers a gorgeous view of the surrounding area. A former lighthouse is open for tours.
Old Town – The birthplace of San Diego, this historic district includes preserved buildings and icons of the Spanish heritage of San Diego and the Old West.
Downtown – The urban center of the city, with plenty of restaurants, shopping, and nightlife, along with several museums, including the San Diego Maritime Museum and the USS Midway Museum.
Hotel Del Coronado – Located in Coronado, this gorgeous hotel was constructed in the late 1800's and is located at the beach.
San Diego Zoo Safari Park – The sister park to the San Diego Zoo. The park covers 1800 acres and is located about 30 miles north of San Diego near Escondido, in the San Pasqual Valley in Northeastern San Diego.
Legoland California, in Carlsbad. Sister park to the Danish park themed to the phenomenally popular toy line. Strikingly accurate Lego sculptures, thrill rides, and more.
Beaches – Along the San Diego County coast one can find a wide variety of beaches suitable for swimming, surfing, and general beach-going. San Diego has several beach communities, and in North County you'll find beautiful beaches in nearly all of the coastal towns.
Gamble - The San Diego area has numerous gaming sites, all operated by local Indian tribes scattered throughout the Inland region and the eastern edge of the North County region. They range from full-blown resorts to one-room bingo halls. Some offer hotels, golf courses, concert venues, and shopping outlets. Barona Valley Ranch, Harrahs-Rincon Resort, Viejas Casino, Sycuan Resort, Golden Acorn Travel Center, Pala Casino, Pechanga Resort, and Valley View Casino are among largest of the many venues. "The big three"; Barona, Sycuan, and Viejas, all feature a distinct policy of allowing those 18 years or older to gamble, while most others follow a 21+ plus rule. Alcohol may or may not be served at some locations.
Wine tasting - In the Inland region, especially around towns like Julian, there are many wineries and orchards open for tours, wine tasting, or fruit picking.
From San Diego County it's easy to make a quick trip down to Mexico. Tijuana lies right across the border from San Diego, easily accessed by car or the San Diego Trolley light rail service. For a more low-key alternative, drive to the small border crossing town of Tecate (home of the Tecate brewery).
The many attractions of Los Angeles and Orange County are relatively easy to get to via a drive on Interstate 5 or along the Pacific Coast.
There are no boats to Catalina Island (Avalon) within San Diego County. You'll have to go north into neighboring Orange County to the pier at Dana Point. By car, take I-5 to exit #79 Pacific Coast Hwy 1 (make reservations).
Temecula Wine Country is located north of San Diego County along I-15 and makes a good day trip. There are about many vineyards (with tasting rooms) located fairly close to each other. One hour further is the mountain resort of Idyllwild which features shopping and outdoor activities in an alpine forest.
This is a usable article. It gives a good overview of the region, its sights, and how to get in, as well as links to the main destinations, whose articles are similarly well developed. An adventurous person could use this article, but please plunge forward and help it grow!