The boat tours no longer have the crazy-complicated pricing system described in the book. It’s simply M$780 for a one-hour tour and M$1380 for the two-hour tour. That includes park fees.
Alberto Rodriguez is no longer reachable by email, but he is still leading birding tours, and can be found at the parador (the boat launch) nearly every day.
Ria Celestun hostel is shut.
And biggest news of all: there is now an ATM in town.
Also note: the back road described on pp. 239-40 is now in extremely rough shape. The stretch south from the Celestun highway to Chunchucmil is incredibly potholed and rough–I did get through in a tiny rental car with no damage, but it was slow going, about 20km/hour.