I have the same issue. My cats love to eat the lower fan leaves...I allow it to happen tho, so I ain't complaining. Mainly because they provide hours of entertainment chasing each other around the plants, hiding behind them. Its really funny.
The problem with cats is that they are a pain to train. The previous post about the spray bottle is good advice, cats hate getting sprayed, freaks them right the fuck out. You could also try bitter apple, its a product available from pet stores and has an extremely bitter taste. I would think that spraying your plants foliage with this would be a good passive way to insure they leave the plants alone. The spray technique is awesome but you gotta be there to see it. The bitter apple is always on the leaves and I dont think you would have to apply it for very long.
CK