We have a plan worked out that we are going to take a bus from Playa Del Carmen to Chetumal transfer to Corozal and fly to San Pedro, however we will be coming from Cozumel. Is it imperative to make reservations on the ADO busline? I have tried it on line through ADO and Ticketbus but the site doesn't go to a booking page. I don't want to make a special trip over to Playa while we are in Cozumel just for the bus tickets, but if I have to I will. Any Suggestions?