Should I cut all my plants back now or wait.

I would wait a while for warmer weather to see if the roots are still viable and will start growing new shoots. Pull off anything that is rotten and soft, but leave anything that looks viable, just in case. If you are going to get that cold, cover your susceptible plants with sheets, no plastic unless it is a bucket, which is another option to cover plants that fit under the bucket. I hope some of your plants do come back for you! Most of what you have down in South Texas would be annuals for me that would have to be potted and brought in for at least six months! I lived in the Galveston area for four years and loved the warm winters. People thought I was crazy when I wore nothing warmer than a light fall jacket all winter. They were all wearing wool maxi coats, gloves, hats, scarves, etc. because they were so cold.

If you cut back before spring is truly around the corner, new growth may start and then it will be susceptible to freezing ... the plants could then die more readily than if you let them alone for awhile. In addition to the suggestion to use buckets, I used cardboard boxes ahead of unusually cold weather here in central-east coast Florida. I didn't have to worry as much that the plants would get as hot as they do under buckets or big empty pots (which I've also used) if it warmed up a lot during the day. To hold in place, I used purchased "garden staples," plus made some more out of pieces of wire coat hangers.

I have heard that you should wait to see what comes back. even though parts may appear dead, sometimes there will be surprising new growth.

I would wait until the last frost passes