Yes you could do well planting one now, I have one that may fruit this year, planted it last winter. Most if not all peaches and nectarines are self fruitful so no pollinator needed. The genetic dwarfs apparently arent quite as tasty as the full sized (or semi-dwarfed) selections. You may want to choose one on taste instead of size, then keep it pruned back hard every year.

I planted a dwarf 'garden beauty' about six weeks ago, and was told it was self-pollinating. I have it growing as an espalier against a south-facing wall. It's in a sheltered position under the eaves which hopefully will protect it from the strong gales we have passing through from time to time, and keeping the leaves dry is supposed to help prevent 'peach leaf curl'. Right now, I keep forgetting I actually planted it for the fruit, as the blossom is such a gorgeous deep pink it is more beautiful than a lot of my ornamentals!

I was found mine at Enchanted Way Nursery in Simi Valley - all their deciduous fruit trees were on sale at 40% off!

Good luck.
Provence

Depending on where you live in Southern California (look up your Sunset climate zone), you may need to consider chill requirements for stone fruits. Below is a link concerning low chill fruits. As bfreeman notes, you can also plant standard varieties and keep them pruned small.

Nectarines and peaches require more spraying during winter for fungal disease, especially near the coast, than most fruits (though all stone fruits should be sprayed in fungus-susceptible areas, with at least one treatment including dormant oil to kill insects. Apricots, cherries, peaches and nectarines may also require spraying if they bloom during wet weather.) Nectarines and peaches generally require summer heat for good flavor.

I prefer to concentrate on plums, Pluots, apricots and peaches, since these are easier for me to grow and harder to get with decent quality commercially. But some of those nectarines and peaches with showy flowers really are attractive. Here are some descriptions of nectarine varieties.

http://www.davewilson.com/br40/br40_trees/br40Nectarines.html

Here is a link that might be useful: low chill fruits

I planted a bareroot apricot and a bareroot nectarine February this year. Neither one has no leaves. Some branches appear to be dry but the main stem is still green. Are they alive? I live in orange county SoCal.