Overall I like all three.
1) I agree that the horizon is tilted ever so slightly. For future reference I think a shot like this would benefit from a polarizing filter. Another thing to keep in mind is that putting the horizon right in the middle of the shot generally makes for a less interesting shot, though here I like the placement.
2) I really like that she got down low for the unconventional perspective. Trying to change the angle to eliminate the car's undercarriage ( or add more of the pole) would diminish the effect of the perspective. It may have benefitted from some fill flash (or better yet some reflected light) since this side of the car is in shadow (due to the backlighting, which I like).
3) My favorite of the three. I really like the composition here - placing the horizon low, placing the ice cream truck low and to the side. I also like that the truck is on the right, as though it's ready to leave the frame, rather than on the left as though it just entered the frame. Very well done.