Still not sure if It's Always Sunny in Philadelphia is for you?
I've done my best at assembling a variety of clips from the show that will give you a sense of the program's humor.
The better clips are from Hulu below (beware, because the show is rated MA, you must have a Hulu account and be logged in to view them):
Dennis resembles a child molester: A Problem for Dennis
Dennis tries to sleep with Mac's mom: Dennis Hits on Mac's Mom
Charlie's Intervention (everybody mistakenly believes he was molested as a child): Where Were You Touched
Trying to collect welfare: Crackhead and Retard
Also, for international viewers or people that don't want to bother creating a Hulu account, here's a few YouTube clips: