The advantages to do late summer vegetable are:
1) Much less bugs in late summer comparing with late spring or earlier summer.
2) The weather is not that hot/dry in late summer and fall, will need much less water.
That means the late summer vegetables are much easier to take care.
It is good time to start late summer vegetables now. You can do the following late summer vegetables:
1) Radish: you should start now
2) Baby Bao Choy: you can start seeds now, and transfer the plants in 2-3 weeks when the plants are ready.
3) Garlic: you can start in the middle or later of August.
Above are my experience, and I have been doing that for several years. By the way I live in Zone 5.
