If you're arriving in San Diego by bus, train, or cruise ship you're likely to be getting off in Downtown. Even arriving by plane basically puts you in Downtown, given how close the airport is to the city center. Detailed info on arriving via those modes can be found in the Get in section of the San Diego article.
By car
Downtown is served by three freeways. Be warned though, Southern California is notorious for its confusing interchanges and freeway systems. You may exit off the freeway thinking you're going one direction, when it fact you'll find yourself heading in a completely different direction. So careful examination of a street map is recommended.
I-5
wraps around downtown to the north and west, providing access from the north and the south. From the north, the Ketner Blvd. exit will provide you with the most direct access into Little Italy, while the Front St. exit will be your best bet for getting right into the thick of downtown. From the south, exiting onto 19th St., which acts as a frontage road to I-5, will get you to a number of east-west streets, including Market St., that upon turning left onto will take you right into downtown.SR-163
enters downtown from the north, turning into 10th Avenue/11th Avenue in downtown. SR-163 connects downtown to the northcentral and northeastern areas of San Diego.SR-94
connects to areas east, and turns into F Street/G Street upon entering downtown.Downtown is easily accessible and traversed by automobile, but it is one of the very few areas of San Diego where it makes sense to get around by other means. Parking is expensive and can be very hard to find during special events like Padres games at PETCO Park. You can park at the garage at Westfield Horton Plaza for free for up to 3 hours as long as you validate the ticket at the small validation machines inside of the mall.