Bruce,
I’m not Phoenix, but I can answer a few of your questions.
I did a quick search online and found a few in your area. You may also wish to look at this older post on the site with some references for Jacksonville. There are a ton of mattress stores offering latex in San Fran when you visit there. Just do an online search.
Latex works great on a power foundation, and it is all I recommend for use with a power foundation, as it puts up very well with the specific weight concentrations and demands of an adjustable bed base.
Most all-latex mattresses do not use a racetrack or perimeter polyurethane foam edge reinforcement system, as people are usually attempting to get away from polyurethane foams when looking at an all-latex product. While the edge of an all-latex mattresses will feel soft when sitting on it (latex is very point elastic), the edge itself will hold up well. You can find mattresses out there that use polyurethane support cores or innerspring support cores that do have harder edge support systems.
Sorry, but I am not familiar with that brand. I can’t even find a record of it. Maybe you have the spelling wrong? Did you mean Zenhaven? It has been discussed quite a bit here on the forum (just do a search), but testing out different latex mattresses in stores won’t tell you how that mattress feels unless you’re able to put together something that has the exact same layers at the same thickness and same ILDs, along with the zoning that their core has. And frankly, if you’re looking to shop online, there are more affordable and more configurable latex options.
It’s not a dumb question - I get it a lot here. Two twin XL mattresses are easy to make up with the mattress pad and fitted sheets. Lifting up the head can help out. Use king sized sheets, blankets and comforters.
I hope that helps!
Jeff Scheuer, The Beducator
Mattress To Go