Hi sqls,
The Telluride uses higher quality materials and would likely be better value than the Lady Americana you were looking at. 1.8 lb polyfoam is a higher grade of polyfoam than what they likely use in the Lady Americana (which is probably 1.5 lb polyfoam) and latex is a premium foam and higher quality than even the best polyfoam you will likely find in any mattress. These are all higher quality materials than you would usually find in a mattress in this budget range.
While I would normally be cautious with a mattress that used this much polyfoam in the comfort layers … the higher grade and the fact that it also contains 2" of latex relatively close to the top would provide better durability and value than other similar mattresses where the polyfoam was a lower density and more subject to early softening. My biggest “caution” with this mattress would be the thickness and softness of the comfort layers in combination with a high gauge pocket coil which would make for a fairly soft mattress which may have some potential risk for best alignment but your own careful and objective testing will tell you more about this than anything else.
You can read a little more about “soy based” or other so called plant based foams in post #2 here. As you can see … it is basically just polfoam which has replaced a small part of one of the chemicals used to make it with a plant based chemical derivative and would be comparable to other types of polyfoam at the same density. I believe it is also 1.8 lb polyfoam but they could confirm this.
If you do end up going in this direction … I would make sure that you had slept on it for long enough to break in the mattress and go through any adjustment period you may have before considering a topper to make it softer yet.
Phoenix