I'm in the subtropics of SE Queensland, Australia. No frosts or hurricanes here. We get a long dry spell followed by plenty of rain mid to late summer. I'd guess that it's a similar climate to coastal Florida.

Ice cream bean grows really quick here & doesn't die back in winter. I have a Moringa growing but it doesn't seem to love where it is right now. I've put cuttings of it into my Syntropic system. Better to over plant than under plant. I didn't think Moringa was a nitrogen fixer but it makes sense given the nitrogen content of the leaves. 

I've been looking at Tithonia Diversifolia (Mexican Sunflower). It seems to fix nitrogen & produces a lot more bio mass than Moringa. There also seems to be both sterile & fertile varieties & I don't want it spreading by seed. Both varieties readily root from cuttings or fallen stems so even the sterile variety can be hard to control. 

 Oh I'm probably just wrong about the moringa nitrogen fixing then. I've got a packet of the tithonia rotundifolia waiting out for spring. 
I tried red cowpeas for a cover crop but we have a huge issue with invasive Russian bindweed here, as well as it's cousin morning glory, and they just took over the field. I learned from it though and have better plans for more direct watering next season that I think should help.