Albuquerque International Balloon Fiesta in Albuquerque, New Mexico. It was last week. It's a pretty crazy event. You get to the gate at 4am and there is already a line to get in (gates open at 4:30). They start inflating the first half dozen balloons about 45 minutes before sunrise. They call it the "Dawn Patrol". Once they are off and the sun has started to rise balloons start going up in earnest. Something like 850+ balloons over the course of about three hours or so. By 11am it's done and everything closes down until the afternoon when they have the "night glow", which is a few dozen balloons filling up and firing off their burners to make the balloons glow in the night. No launches at night though. They do it every year, you should try to catch it. You can stop at the Grand Canyon on your way back.
BTW, the main event sponsor is Canon.
They have a balloon event here in the desert also. I believe it is in February.
Not so far to drive!