I have to second that the cage is too small for an adult dragon. A 30" long cage is maybe a 30 gal long tank which is way too small. It should be more like a 55 gal long or bigger, but definitely at least 4'x2'x2' in size as BDLvr pointed out.
Seeing a female across the room certainly will get your male dragon worked up and running around his cage trying to find a way out to get to your female, is one good indication he is more than ready to breed.
I suggest getting a bigger cage, moving your male or female into a different room and try and clean up poop as soon as possible (though I know if you are gone all day and it is during the day he typically goes, can't really be there to clean the cage right away. But if you see it in the morning before leaving, clean it up right then. Less chance of your dragon running through it if its gone as quickly as possible.)
As for greens, i find placing them more centrally in the cage and having a clear 'path' around the cage ensures it is less trampled through than if the food dish is placed in a open clear area.
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PHLdyPayne