From San Diego, using your motor vehicle, take the I-5 or I-805 bound south to get to Tijuana. When you arrive at the border, you can either park and walk or continue driving to Mexico. Expect frequent inspections (due to trafficking of firearms). On the other hand, driving from Mexico to the US will result in a long wait, especially during the holiday weekends and the evening rush hours.
You can also get home to the US through the Otay Mesa and Tecate border crossings which can be less congested. However, going to Otay can be risky and not advisable at night. Border officers aren’t as amiable as the ones at San Ysidro.
The pedestrian lane returning to the US may be lengthy, but you can try vans and bus lines that cross the border. Agents will offer you a ride aboard vehicles back to the US will ask for USD $5-10/person to let you board.
Buses are advisable for travel in the immediate areas like San Diego, Mexicali, Ensenada, and Los Angeles, among others. Farther destinations in Mexico are best traveled by plane.
The main bus station is located south of the airport (8.5km), and can be reached by taxi from the city center or by bus from Calle 3. Bus companies such as Greyhound, Crucero USA, ABC (Autobuses de la Baja California), and Grupo Estrella Blanca can be accessed.
The US-bound buses cross the US at the San Ysidro main border crossing. They have a special lane which bypasses the long lines to cross the US. The passengers are inspected once they are dropped off into the customs building. Upon clearing immigration, they are picked up at the San Ysidro bus station (San Ysidro Boulevard behind McDonald’s & Mercado) for the trip north-bound. If headed south, there are immigration checkpoints 30-50km ahead. Prepare all required documents such as the FMM card (tourist card).
Arriving thru a bus line will cost between USD $12-20 to take a taxi to the border. However, taking a bus is only 10 pesos. Once you’re at the crossing, there’s a San Diego trolley in front of you that can take you straight to the airport or downtown. It will cost you US $2.25 for a one-way pass.