Compared to so many foreign VIPs in town this week — who are tying up traffic and restaurants with their over-the-top security squads — Mexican billionaire Carlos Slim cut a more slender swath. The world’s richest man took in a performance of “Spider-Man: Turn Off the Dark” Wednesday night, and he went backstage to greet the cast with “zero security” and “just two friends” in tow, according to a spy. “[Slim] said the show made him want to act,” said a backstage source. “We told him to stick to telecommunications — there’s more money in it.” Slim was also seen Monday night entering a Metropolitan Club gala with no entourage at all.