Can I grow canna's there?

They'll probably grow there if the soil is decent and they get water.

Is there a difference in height between the deck and ground you'd plant them in? If it's a raised deck I would think that in time the canna's would try to spread under the deck.

Are you wanting a tall or short canna? Some of them get wider than others, so they may take on a look of being pushed over by the fence. I think you'd want to try and find a canna that doesn't get very wide.

I don't know where you're located, but Canna's are pretty tough all long as they get water and some fertilizer now and then. My biggest concern would be heat reflection from the pool deck causing leaf burn.

What is the fence and deck made of?

The pool deck is made of acrylic and the fence is metal. Maybe I can take a picture and post it here. I have a lot of landscaping to do. Thank you so much for your help!