Sure, I'd go back, unless he specifically asked me not to. Otherwise I'd figure he was showing me so we could share But I certainly wouldn't tell anybody else.
If he is a really good friend then I would not do it without asking him first. Even though it would be a public place the friendship would be worth the gesture of asking him to okay it.
Any time we show each other those "secret" spots it is with the intention that they will use it themselves, but just the same, I always ask if they would mind me going back.
I think many of us are in agreement here, but for me most times I will tag along fish with my best mate and he is okay with that. For us, its just time to catch up since I am not that good with a pole in hand.