You can also apply it on latex balloons. However, this is a bit trickier because latex balloons are "rounder" (i.e. have a stronger curve). And latex balloons will loose air (or helium) faster and therefore shrink faster than foil or bubble balloons.
It takes a lot of practice to get the vinyl properly onto the latex balloon.
The video below is a great tutorial. The instructor shares a really good tip at around 6:50 minutes into the video: she repeatedly cuts the transfer paper up to the vinyl letters so that it curves easier around the balloon.