I have the most success planting in a soggy bed, my neighbors might think I am crazy planting in the rain. I try to keep things light-textured by not compressing the dirt and sprinkling dry compost-rich planting mix around in the planting holes so it's not totally compacted mud in there.
Pea

I'd wait a week.

What ever you decide, be careful to avoid compacting the soil with your foot traffic--putting down a board or several layers of cardboard to step on to distribute your weight reduces compression. Plant roots need air and compressed soil reduces performance.

I'm in Livermore and waiting until next week. It's difficult to backfill well around the roots when the soil is wet and in big sticky globs, not to mention the problems with compaction referred to by hoovb. The first of the year is not too late for installing plants and taking advantage of the wet season for them to establish.