The official U.S. Geological Survey coordinates are 32°40′42″N 115°38′21″W / 32.67833°N 115.63917°W / 32.67833; -115.63917: this defines a spot near the intersection of State Route 98 (SR98) and Brockman Road.

The community is named for Mount Signal, a summit about 5.5 miles (8.9 km) southwest, inside Mexico.

Even though Mount Signal appears to be in the United States, it is actually located on the Mexican side of the border.

It is believed the school no longer exists; its location was one mile (1.6 km) north of these coordinates on Brockman Road.

Federally, Mount Signal is located in California's 51st congressional district, which is represented by Democrat Juan Vargas.