The location is important. Over your heart is a sentiment that would not be lost and would easily be concealed if you wanted to not show the tat. Your leg would mean wearing pants or high socks to cover if you chose to. If covering the tat is not an issue nor would ever potentially be one, I see no reason why you should not put it there.

I do suggest visiting several artists before choosing one. Look at their artwork and take into account not just the drawings on the wall, but the body art. Lines should be smooth and even, is the ink applied with the right amount of pressure. (too much or too little is a common problem I've seen) Also, if positioned on your chest you don't have the wrap around factor. Some of the artwork I have seen on legs or arms appears distorted or skewed. A good artist knows how to work around that.