Really fall into winter is the best time to plant things in California except tender subtropicals. The cold is insignificant to things that aren't tender, although you won't see much top growth at this season. The rains are only a problem if you are trying to work the soil while it is too wet and you have clay, but if you wait to dig until a few days after a rain event, you shouldn't have problems with compaction, just easier to dig soil. I find that gardens I put in with November thru February planting dates are some the fastest to get established, and easily outgrow the same sized plants planted in spring, if measured a year later. They also tend to have deeper rooting as they followed the moisture of the rains and root more widely and deeply. The only drawyback is that it is colder for US to be planting now, so dress in layers or wait until it warms up in the afternoon to go out and plant.

If you are talking about planting out winter harvest vegetables at this time of year, you are a little late to get things you can harvest in late winter, and they may not be ready to harvest until later in spring, which might interfere with your intended spring vegies if you lack sufficient space.

It will also make a huge difference on how much sun your planting area gets in winter. If it is totally shaded, you shouldn't expect to see much in the way of above ground growth on anything but the hardier winter growing plants.

An excerpt from the current Garden Company (Santa Cruz) newsletter:

This is a great time of year to plant low growing ground cover to help stabilize soil and choke out weeds. We have dozens of possibilities we can show you in a wide range of mature height, leaf textures, and flower colors.

There is still time to plant bulbs for spring bloom. Shorter days and cooler temperatures will help prevent the bulbs from sprouting prematurely. We still have a good selection of Tulips, Daffodils, Bearded Iris, Watsonia, Muscari and many others.

Pull out your tired summer annuals and plant winter blooming bedding plants like Calendula, Primrose, Iceland Poppies, Mums, Pansies, Violas and Cyclamen.

Our fall and winter seasons are sooooo overlooked for vegetable gardening. Hey, we live in paradise, not Kansas. This is the perfect time for planting root crops, leafy greens and head crops. We have a great selection of carrot seeds, onion sets, garlic bulbs, and shallots as well as seeds and certified organic 6-pack starts of lettuces, spinach, chard, kale, broccoli, cabbage, cauliflower, Asian greens and much more.

It would be a good time to give perennials a light pruning if they have finished blooming. This will remove spent flowers and keep plants from getting too leggy.

Clean and fill those bird feeders. Fall brings increased activity from hungry Finches and other wild birds. Medium Sunflower Chips and Nyjer Seed are Finch favorites.

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I suggest that you watch the weather and protect, especially, your newly planted babies from freezing, or ask at the nursery for particularly hardy selections. Also, be sure to water if there is a warm spell, or no rain for long enough to dry out your plants.

A strawberry farmer that I know puts in his strawberries this time of year. Then they bear all spring and summer.

This is also the ideal time to prepare the soil for rose planting. New bare root roses will arrive in the nurseries in December, and you will have the best selection and highest quality stock available. Roses are happiest, here, planted in winter, as they put on root development for a few months that support greater growth next spring.

Bare root fruit trees are available as well.

Any areas that you want to plant in spring can be sowed with a green manure crop, which is turned under when it's time to plant in spring, fertilizing the soil.

Thank you for both replies! I am hoping to get several shrubs (mostly Westringia) and maybe a tree (Nyssa Sylvatica) into the ground to take advantage of the rain this winter.