Hi Ket2593,
The first place to start your research is the tutorial post here which has all the basic information, steps, and guidelines you will need to make the best possible choices.
A mattress is only as good as its construction and the quality of the materials in the mattress and brand shopping is among the worst ways to choose a mattress. I would focus on the construction and materials in the mattress regardless of the name of the manufacturer on the label.
I don’t keep a list of specific types of mattresses in each area or at each store but some of the better options and possibilities I’m aware of in the Greensboro area are listed in post #2 here and if you check their websites or probably better yet call them and tell them your criteria and what you are looking for they can tell you whether they have any latex/innerspring hybrids on their floor that you can test.
Phoenix