If you play Late Night and find there are no visitors to your clubs in town, this small fix may help. Credits to someone on the official TS3 forum.
Open the file GraphicsRules.sgr in C:\Program Files (x86)\Electronic Arts\The Sims 3 Late Night\Game\Bin
Just as in Sims 1, the game's CPU detection is faulty and it will set many people's systems to very low, even if you a very good chip\s.
When set low, it only allows a very few Sims on a Community Lot at once.
Works fine with AwesomeMod and Twallan's mods.
If the NPC Sims are having too much fun at home, they will not go to clubs. So go to any houses of Sims you are not currently playing and want to turn up at the clubs, and remove some or all of the "fun" things.
(The same principle applies to gyms, etc - if their homes are full of exercise equipment, Sims will not turn up at the community gym.)