You can grow walnut trees in the south of Florida.
In fact i think you might even have wild native walnuts there like Juglans Jamaicensis thats native to Cuba and Jamaica.
Also juglans Neotropica,a few otther south american and mexican walnuts would do well and from the same genus,Oreumunea sp and Alfaroa sp.
Somme south asian juglansaceae would do well also in that warm weather including the probably extinct ,or nowhere to be found now,vietnamese beaked hickory ( wich shares traits with hickoryes and walnuts).
All these trees how ever,are highly endangered and it would be really hard to get a few seeds.
They are all edible and tasty just as the carpathian walnut,but they have thicker shells.
As for plums,there is also the african plum ,Prunus Africana wich can grow in tropical places but this is also highly endangered and would be impossible to get seeds.