There are few things more photogenic than a mass of hot air balloons. I shot the Albuquerque International Balloon Fiesta a few years ago and it was absolutely spectacular.
I don't know about your venue but, the public is permitted to be on the balloon launch grounds before, during and after the launch. Shots of filling the balloons are very photogenic. Of course, if you are allowed on the grounds, the actual launch and flyover is great to shoot.
A few things that I learned:
1. Be cognizant of the wind direction. Obviously the balloons will fly in the direction of the wind so you want to be able to intercept them.
2. I shot with a 12-24mm f/4 Tokina and a 24-70mm f/2.8L on a pair of Canon 1.6x DSLR cameras. This was a great focal combination.
3. I shot everything hand held and most often used from ISO 200 - ISO 800 depending on the lighting conditions. A shot in programmed exposure mode. I used no flash but counted on the flame from the hot air generators to light my images.
4. Bring a CPL filter but, don't put it on your camera until after full light. Don't use a UV filter because then you will have to remove the filter as you get ready to place the CPL on your lens.
5. If your camera has the capability to easily shoot AEB (auto exposure bracketing) choose that. I can set up my Canon cameras to automatically shoot 3 images in burst mode with correct exposure, and plus and minus exposure. The number of f/stops to be bracketed is part of what you decide on when you select AEB. I shot with one stop bracketing. Most of the time I was right on with the normal exposure but, occasionally either the plus or minus one stop exposure was the best.
6. Bring enough memory so you don't have to restrict your shooting.
7. Wear layered clothing. It was cold as heck before dawn in Albuquerque (October) and got quite warm after the sun came up.
8. If you can ride in a balloon, great shots can be had from above other balloons with the ground as the background. To me, shots like that are more interesting than shooting with sky as the background.
See additional Albuquerque Balloon International Balloon Fiesta images at:
ALBUQUERQUE BALLOON FIESTA 2007 - rpcrowe's Photos