New to KC and Costco is literally across the street. Will they let me shop as visitor or guest to see if I like them better than Sam's Club?

Certainly! With them being right there, it will probably be worth the membership just for the convenience! But the choice is yours. Best wishes!

Definitely!

Yes.

You can get a guest pass at membership and shop for the day

They will not let you shop on a guest pass, only look around. I found everything comparable to Sam's club and Sam's membership is cheaper for veterans.