Could you go to a nude beach or resort with a friend of the opposite sex?

I most certainly could. I'd take that opportunity in a heartbeat, and so would most of my friends (who largely tend to be girls anyway).

The chance to pick each other's brains on the beauty and attractiveness of the people we see would be an almost once in a lifetime opportunity.

Sure I could and it wouldn't alter a thing in the relationship. That doesn’t mean I won't have a picture of them naked pop into my head from time to time but that wouldn't have any ill desired effects.

MY opinion, not yours.

Cheers.