What to plant in August

The two fall-blooming bulbs I have success with are:
Crocus satirus
Haemanthus albiflos (aka Royal Paint Brush)

I would plant them (in San Diego) now.

Crocus grows in full sun, Haemanthus needs partial shade -- or mostly shade if you are past the coastal marine layer belt.

There are several local suppliers who specialize in bulbs. The one I am familiar with is:
Mary's Garden
610 Sunrise Drive
Vista, CA 92084
760-724-1500

You might also find this website interesting:
www.easytogrowbulbs.com/

Would it be a good idea to plant something like butternut squash in August or early September?