Hi brandislee,
The first place I would start is the tutorial post here which has all the basic information, steps, and guidelines that you will need to make the best possible choices … and know how and why to avoid the worst ones.
The tutorial post also includes a link to the members here that sell latex mattresses online that include a wide range of options and budget ranges (including a number that would fit inside your budget).
A forum search on Plushbeds will bring up more information and feedback about them.
You can read more about Saatva in post #1 here and a forum search on Saatva (you can just click this as well) will also bring up much more information about them.
The better options and possibilities I’m aware of in the Minneapolis area are listed in post #2 here (including diynaturalbedding who as you can see from their posts are very knowledgeable and would definitely be worth a visit :))
Phoenix