I am 5'7" my bust is 34" and my waist is 28" so I would be a size 4 if I went with my bust size and a size 6 if I went by my waist size. If you are in between sizes like this, go with your bust size as the waist isn't at all fit. Both the size 4 and size 6 dress hit the floor when I wasn't wearing shoes. 2 inch heels would work well with the length.  I've included pics. The teal is the size 4 and the coral is the size 6.  The size 4 fits perfectly. This is for a bridesmaid dress on a beach which I think will be perfect.  It is very well made for the price.  No complaints.

update 3/13/18: I returned the coral in a size 6 in exchange for a size 4 and it didn't fit well at all. The fabric over the right breast was loose and droopy.  I'm returning this for another size 4 and hoping the fit is more consistent to what the size 4 teal dress was.