Hi blilly,
It’s very unlikely that you will find any “all memory foam” mattresses because memory foam is a comfort material and isn’t firm enough to use as a support layer for a mattress. Memory foam mattresses will all have some type of firmer support material under the memory foam comfort or transition layers (usually polyfoam but sometimes an innerspring as well).
Latex and memory foam are very different materials so it’s possible that you may like the “feel” of latex although of course each person can have very different preferences than someone else. There is more about how memory foam and latex compare and the pros and cons of each of them in post #2 here but the best way to know how you feel about latex (or any material or type of mattress) is to test some latex mattresses that use different types and firmness levels of latex.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses but I would tend to avoid any major brand mattress or any mattress that has more than “about an inch or so” of either lower quality materials or “unknown” materials which would likely be a weak link in the mattress in terms of durability (see the guidelines here). Buying any mattress where you can’t find out and confirm the quality and durability of the layers inside it (see this article) would be a very high risk purchase and is one of the most common reasons for foam softening and breakdown and the premature loss of comfort and support and the buyers remorse that goes with it much too quickly after a purchase.
The only way to know the quality and durability of a mattress is to make sure you know the type and quality/density of the materials inside it and it’s always much safer (and usually more accurate) to assume that any unknown materials are lower quality materials that would be a weak link in the mattress.
The best place to start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choice … and more importantly know how and why to avoid the worst ones.
The better options or possibilities I’m aware of in the Baltimore area (subject to the value guidelines I linked) are listed in post #2 here.
Phoenix