While i do not know anything about shore tours at Progresso, my guess is that It would be advisable to prebook on the ship. From what I saw, there is nothing much in Progresso,( for the most part), only a dock. I talked to some folks who found a small market. I can say that Uxmal is very very good. Far better than Tulum! It and Chichen Itza are the best Mayan sites in thw world from what i gather. A few years back, I took a combo tour Uxmal in the morning (lunch included) and Merida that afternoon. that was likely the best shore trip that I have ever taken. If one loves history like I do, then Uxmal is worth the money!!