Karen,
I had a greenhouse in NC with an inch of gravel everywhere except for cement pavers down the path. That really helped retain humidity and if you had a swamp cooler I think you would be all set. I grow mostly Catt's and they are quite flexible..my night time temperature was set for 60 during the winter and sometimes in the early spring it would get pretty warm ... I had a few over 100 degree afternoons in a row and the plants didn't complain (much)!
