The LV vault store is about a $20 ride from center strip, like the Bellagio or Paris. I would say if you are comfortable, take the bus to Binions in Downtown and go from there by cab. Its a nice store, but slightly small, like most O-Stores. If you have some extra $$$ and time, check it out if you have never been to a vault. They have some cool old stuff but only a small selection of new merch.
Enjoy the city!