Hi JD2K,
The topic of memory foam and sex is a “hot” one but I think it would be fair to say that there is general agreement that it certainly is different from lovemaking on more resilient materials and that memory foam doesn’t provide any of the bounce or “energy” return that most people are used to and that contributes to the “rhythm” they are familiar with. Sex on memory foam takes more “effort”. It’s also more difficult to use certain positions because there is less “traction” or support for knees, elbows, and hands pressing into the material.
Some people don’t ever get used to it, others learn to experiment and adapt with different positions or styles, and others yet may even come to prefer it. Like almost everything else, there is no general consensus but I think that a majority of people would say that more resilient materials such as innersprings, latex, or polyfoam are more “sex friendly” than memory foam with a smaller but vocal minority disagreeing 
There is also some information about mattresses and sex in this topic as well.
If you let me know your city or zip I’d be happy to let you know of any of the better options or possibilities I’m aware of that may carry latex mattresses in your area.
Phoenix