I'm on the fence with Ugly Americans. I think the premise is great and has lots of potential, and there are some good jokes here and there, but the characters, for the most part, are just there. None of the cast members are particularly engaging or likable; they go out of their way to show them as jerks, deviants, drunks, perverts or whatever, but there's no redeeming warmth or personable side to any of them. The lack that something extra that makes you care about them.
Plus, the characters don't interact with each other much; Mark interacts with each other cast member individually, but there's no rapport between any of the other characters, plus Mark himself is little more than an audience avatar.
If UA put a tad more work into its' cast and the writing could tighten up just a bit, I'd be more on board with the show.