Hi sudzy,
The mattress shopping tutorial includes a link to a list of the members here that sell mattresses online (in the optional online step) and many of them sell latex and latex hybrid mattresses that use different types and blends of latex that have a wide range of different designs, options, features, return and exchange policies, and prices. Post #3 here also includes a list of many online manufacturers that sell component latex mattresses as well (with some overlap with the members list).
Mattresses “as a whole” don’t have ILD ratings … only the individual layers inside a mattress. Like many other component latex mattress manufacturers … mattresses.net offers a range of ILD’s in both their comfort layers (which is the biggest part of how soft a mattress “feels”) and support layers. I’m not sure which of their mattresses you are looking at but their adjustable ultra plush mattress has the option of choosing either a 2" comfort layer in 22 ILD or a 3" comfort layer in your choice of either 19 ILD or 28 ILD. I would also keep in mind that the softest latex would be too soft for use as a support core in a mattress so a “soft” support core would generally be firmer than a “soft” comfort layer.
ILD/IFD is also only one of several specs that makes one material feel softer or firmer than another (see post #4 here) and the ILD or IFD of different materials or different types and blends of latex may not be directly comparable to each other (see post #6 here). Every layer and component in a mattress (including the cover) will also have an effect on the feel and performance of every other layer and component in the mattress and on the mattress “as a whole” and putting too much focus on ILD/IFD alone or any other single specification (especially if it’s only a single layer) can sometimes be more misleading than helpful.
If there are any Pure Talalay Bliss mattress dealers that are close to you (their retail store finder is here) then they may be worth testing as a reference point because both their Beautiful and Worlds Best Bed are very soft and use a 3" or 4" layer of 15 ILD Talalay in the top layer (you can see the specs of their mattresses in post #2 here).
Phoenix