The card says, "Once per turn,… [paraphrasing] you may look at the top exploration card of your room." It says "Once per turn…" [not paraphrased], so can I do this once per investigator per round, plus the Keeper's turn because there seems to be no active turn restriction?
For instance, at the start of Michael McGlen's turn (who is completely on the otherside of the map, far from Monteray's room), I look at the exploration card underneath Monteray Jack and find it's a Nothing of Interest and put it back facedown. Monteray Jack then takes his turn when McGlen is done. Monteray Jack decides not to explore knowing the card is useless and moves into Bathroom 2, does his Legacy Map again for his turn and sees it's a Lost Soul card, moves again to the Chapel and moves once more as his action, still in the Chapel. The Keeper starts his turn and before anything else, Monteray Jack looks at the exploration card in the Chapel and sees its an Elder Sign, and places it back facedown.
Again, is this a legimate use of this map's ability, seeing as it requires no action to perform nor limits when it may be activated?