Can you buy a camera lense, and return it a week later?

Well i'm going on a tropical trip, and i want a nicer lens then what i have ( nikkor 35-80mm 5.6D )
but i don't want to keep the lense, so do you think i would be able to buy the lens and return it when i get back?

No that is rude ignorant selfish thing to do.

This depends on the store's policy, but using it for vacation and then returning it is not an ethical thing to do regardless of the store's policy. I suggest renting a lens for a week or two, there are places that rent lenses.

Rental would be better. Two places come to mind:

BorrowLenses.com

Adorama Rentals