Dry camping is your best bet. We stayed 10 days last time with no issues. If you need a pump out (we didn't) there is a service that comes around, along with water fill (not from the same truck
Balloons will land right in front of you at times. If you're a walker you can do so from the area. If not, there's a free shuttle that runs starting early, early morning and up to the last show at night. It has many pick-up points and if you happen to be walking toward one of those points you can wave the bus down and it will stop....very friendly operators.
Staying off-site can be a real pain. You need to coordinate your timing for when the main city Fiesta roads are open. Some close and you can't enter or leave the area until they're opened again. Traffic is horrendous as is parking. The surrounding RV parks really UP their prices for this Fiesta - all the way up to Santa Fe!