FloZach get off the highway at a sign that says "Centre Ville." Flo tells Zach that this means, "This is, like, the center of the town." Can't argue with that. She comments that Ian and Teri remained on the highway, apparently looking for a different sign. Probably one that means, "This is, like, the marriage counseling facility." Finally, Asshat gets off the highway as well. You'll notice that Ian just picks an exit and says they'll "try to make [their] way to the mosque." It's not like his contempt for Teri's suggestion that they get off the highway earlier was based on any notion that he knew where they were going. In Casablanca, Flo and Zach ask for directions, while Asshat gets a taxi to lead them. FloZach does indeed beat Asshat to the mosque. So much for it being a mistake to get off the highway, there, Ian.
When FloZach has retrieved the clue, they go to leave, and they run into Asshat and their lead taxi, who are on the way in. Flo doesn't know that Asshat necessarily wants the taxi again, considering that the teams are traveling by car and not by taxi, so she goes over and asks the driver if he'll lead them to the train station. The driver doesn't seem to think he's working for Teri and Ian anymore either, since he negotiates arrangements with Flo and they appear to have a deal. Ian catches wind of this and storms over to the driver to tell him not to take Flo and Zach. Understandably, this irritates Flo, who protests, "No!" because she thinks Ian is trying to screw her up and interfere. "I hired this cab, he's mine!" Ian snarls at her. Teri, despite the fact that she doesn't really understand what Ian is doing, takes her turn as well, turning to Flo and spitting incredulously, "He's our cab, don't 'No'!" In case you ever doubt that Teri is perfectly capable of being just as unpleasant as Ian is, watch that little moment a few times. That's one of my least favorite tendencies that people who are treated poorly by their significant others sometimes have -- even knowing what an ass he is, she still comes out and aggressively backs him when he's being an ass to other people, like it makes it a little bit better if the two of them team up to be asses to the same person for thirty seconds.
Ian orders the cab driver to stay where he is. Teri herself actually has no idea what he's talking about, or why he wants the cab anymore. This makes it pretty clear, incidentally, that Flo had no way of knowing they wanted the cab to stay, since Teri didn't even know. Ian says to Teri, "I want him to stay here." Teri points out that they can get another taxi. "I. Want. Him. To. Stay. Here," Ian says, just as if his wife is his four-year-old child. Flo, meanwhile, is licking her wounds over the unnecessary snarling. "You don't need to yell, that was really rude," Flo calls over to them, horribly whiny in her delivery but absolutely correct on substance. "I didn't know that was your taxi."