Lake Havasu City, AZ at least 500, I took pictures and people were packed in like sardines, they had to stop car traffic over the bridge due to all the people. Given our max population is 50,000 at the height of snowbird season, this was pretty significant turnout.
http://picasaweb.google.com/charlan46/Havasu?authkey=Gv1sRgCJXQ3p76zMi73QE#5325129803657576562