I grew up on a ~2 acre property in so cal (south OC, near where I am now), and we had a gopher problem but nowhere near this level (maybe 20-30 a year). We used a combination of traps, gas, noise beeper stakes, and poison at the time, but continued to have problems. In an act of desperation, in the mid-late 90s we bought a bunch of those "gopher plants"... the plant multiplied on its own, spread around the property, and we noticed the gopher mounds began shifting away. After 3-4 years, the gophers just.. disappeared...
This may of course just be a coincidence, there could be other factors at stake, but perhaps it might be worth a shot to look into this plant?