Well, I would suggest you DO NOT exchange USD to MXP at Logan, as you will be hit with horrible Exchange Rate and/or Fee for doing it.
Best Option for me has always been using my Bank of America Debit Card to get MXP at Santander Bank Mexico ATMīs, as there is NO withdrawal fee for doing it and you get a competitive interbank rate. It will be way better than in Logan or any US Exchange Place. Second Option if you donīt bank with BOFA, will always be the exchange places all over 5th Avenue at PDC. They do not charge fees and you can always compare a little while walking and enjoying PDC before getting MXP. Only change at the airport the exact amount needed for ADO bus. Remember Mexico is now strict on accepting USD, but small amounts for buses and convenience stores (and of course Starbucks) will always be accpeted.