Albuquerque International Balloon Fiesta

I have never stayed on-site, but I also cast my vote for that. One thing you might not think about is that depending on wind and other factors, things like the mass ascension may or may not happen. It would be a real bummer to struggle through traffic to get to the park and then have the mass ascension called off. At least if you're on-site, you can walk back to your camper.