A few notes. You can't catch a cab from right in front of Maragaritaville, or any other restaurant, store, shop, or bar at City Walk. In fact WALK is the key word. It's about a mile walk from the parking deck/cab stand to the far end of the complex, which would be Hard Rock Live.
It's a good half a mile, perhaps even a bit more, from the cab stand to Margaritaville. It costs about $16 from the YC to the GF, so I can't imagine it costing under about $35 plus tip from Universal to the YC. And if you get caught in traffic with the meter running--perhaps even more.
Frankly, other than seeing a concert at Hard Rock Live or having dinner at Emeril's, there is no dining or entertainment worth making a special trip to CIty Walk for.
Anne