My sis and I share the membership (2 families) and the yearly fee is covered by the annual rebate we get back. Some stuffs are cheaper than your average grocery stores some are not. Some are cheaper because you buy in bulk but can be more expensive if you don't finish in time and they go bad...I guess it really depends wether Costco is a good deal or not differ base on circumstances.
You don't need a membership to come into the store as they really dont enforce that part of it. They only really check when you check out at the register so it is easy just to go in and look around but the issue is you cant buy anything. The food court is open to everyone it seems.