With all transfer companies you should pre book on line, most don't require prepayment - if you arrive without pre booking you will pay double the pre booking rates because there is a single transportation company that has an exclusive arrangement at the airport. Also, FYI - taxis are not allowed to pick up fares at the Cancun Airport
Book USA Transfers to Desire Riviera Maya Doesn't get better than this - One way Trip to Desire RM $ 35 or Round Trip $ 60 - you can also pay in Canadian dollars, with USA Transfer Canadian dollars are accepted at par value to the USD !!!