Not true. The I-5 and I-15 border checkpoints are about 50-60 miles north of the Mexican Consulate, which is only about 15 miles from the border with Mexico. Those checkpoints are near the northern end of San Diego County, which, along with Imperial County, include CA's entire southern border with Mexico. Those two checkpoints are nowhere near the border.
The Mexican Consulate, 1549 India St., San Diego, CA, is only THREE MILES from the airport terminals at Lindbergh Field (San Diego International Airport), according to Yahoo. The runway is even closer -- about 1 mile.
Clarification: those checkpoints are only about 70 miles from the border. It's close to Mexico when compared to Canada, but it's pretty far when you consider that about three million people live in San Diego County, and most of the county is south of the checkpoints.
Travel through those checkpoints is usually unchecked, especially during rush hour (several hours per day), and the trains are never checked, either.