In So Cal, planting anything except tropicals is best done in autumn as winter rains begin. I'm not a grass person so can't really help you, but also consider Lomandra longifolia 'Breeze' which has become popular in Southern California the past couple of years. It's a male selection so no reseeding. Friends with this plant are quite please with it.

That looks great, I'll check into it. I'm still not even certain that what I have is Mexican Feather Grass, I just know that it's incredibly aggressive and looks just like the pictures I've seen. It's hard to tell from my pic but it is actually huge, about 3-4ft around and about 3ft tall

I have heard that Mexican feather grass is very aggressive in So Cal. I often go and run my hand on my Mexican feather grass backwards against the "grain" and that "Milks" the seed off of them after it has gone past the silky appearance.. That might reduce your problem at the source.. I actually do not get much seeding on my ground here in Central Texas. This grass is more of a cool weather grower and that is when you are wet in your winters at a perfect temperature. Maybe you should look for a warm weather grass that won't seed as much because you will be dry when you are at their germination temperature. M.capilerris does not seed as much for me. but I am not in So Cal. Seeds are what makes grass beautiful but it is also the reason for your problem. Have you asked in the Californian form for a well behaved grass that does not seed out much. Many of the Muhlies are will behaved here.

Yes, that is Mexican feather grass

The suggestion above has been helpful. I've been putting on work gloves and combing out the loose seed strands but the bucketful. That at least keeps them off the ground and out of the wind, though it is currently producing about a bucket per week!