I have a string of Balloons that are attached vertically. Is there a way I can orient them horizontally without starting over?
Select them and move them. They will "slide" around the diameter of the balloon they are attached to (i.e. in your picture, if you select the 16 balloon it will revolve around the 15 one).
You select the balloon, "hover" over it until the movement or four-way arrow cursor shows up, then just "drag" the balloon(s) around the "parent" balloon. It also drags around any "child" balloons. See the below where I reposition the "3" balloon to the bottom of the "2" balloon. This is how things work for me in Creo 4 (and have since Creo 2 or maybe before that).
It depends on the type of balloon you are refering to. If it's a repeat region bom balloon (like Ken Farley is showing), you can drag the balloons around.
If it is a balloon note, I only remember being able to create these as horizontal or vertical and not being able to change them afterwards.