You should be inform your host family of your travel arrangements and estimated time of arrival; in this way your family won't have to wait at home unnecessarily and you won't find yourself waiting outside to get into your accommodation.
If you already speak some Spanish you can of course give this information over the phone.
The following is an example of a letter/email which should be completed and sent to the host family:
Llego a Playa del Carmen el día ..... Mi vuelo llega a Cancún a las ..... y espero llegar a su casa alrededor de las ..... horas.
Dear host family,
I'll be coming to Playa del Carmen on ..... (date). My flight arrives in Cancun at ..... (time) so I expect to be at your house by ..... (time)
..... (Student's name)
Your host family's address When your booking is confirmed, we will send you address of your host family.
Arrival If you are arriving on the Sunday before the course begins, you should make your own way to your host family (unless a transfer has been requested).
Please note You must also let the school know your estimated arrival time just in case the message to the family doesn't arrive.