There is a better technique that works to remove people from a crowded but static scene where somebody is always in the way/background, but the people are at least moving. Set up on a tripod and take a series of photos as the people move around. You need to take enough shots to get at least one shot of every bit of the scene you're interested in. Best to use manual exposure to keep it consistent.
Line the shots up as transparent layer masks in PS and then systematically paint your way through the layers, using only the people-free pieces. Use the one with fewest annoying people as your base layer, and then paint over the people with the corresponding pieces of image from the other layers (which were taken after they moved). Better than cloning them out as you eventually get all the detail that is intermittently hidden.
Another way to do this to use a HD filter and very long exposure to effectively just blur them away (provided they are moving enough)