Hi Georgiagirl,
Post #2 in this thread includes some of the better options in your area including several that make latex mattresses. I would do most of your initial research on the phone telling them about your circumstances, budget, and preferences and asking for their recommendations about which mattresses would be best for you to test. Conversations like this will tell you a lot about the kind of experience you may have if you go there and will help you decide which are most worth visiting.
With heavier weights … more durable ingredients are particularly important. This means higher density memory foams or polyfoams, lower gauge and firmer innersprings, or best of all in terms of durability (as you are already leaning towards) latex. There are some guidelines here about fitting a mattress to different weights and here about different sleeping positions. Because of your larger weights and side sleeping … you will likely do best with thicker/firmer than “average” comfort layers and firmer (and possibly thicker) than “average” support layers as well. Your own testing that is specific to pressure relief and alignment (rather than just overall comfort) using the guidelines as a starting point will help you zero in on your best choices. Some expert guidance from someone who can see you laying on a mattress, is knowledgeable of mattress materials and construction, and has a genuine desire to help you find your best choices (rather than theirs) will also go a long way towards your best choices.
If you have questions along the way … feel free to post them here but you have some very good choices nearby.
Phoenix