Cartoonists will all tell you that the best place to watch people and sketch them is at the airport. There's some folks milling around, but many who take on a single pose for an extended period of time, making them easier to draw.
This airport had more statues than the Uffizi Gallery, and I could have walked right up to any of them and drawn them right down to the last pore. Thanks to the smart phone, people will just stand around in a catatonic state even if an atomic bomb goes off. The only way they would notice is if the blast somehow cut off texting service.