You don't need a visa as such although you do need to fill in a card which the cabin crew will give you before you land. You will be given part of this card back and you must keep this safe as you will need it when you depart.
You will also need to pay a departure tax which is currently £40 (approx) each.

Thanks Denny, been 10 years since our last visit and couldn't remember.

I believe the departure tax has to be paid in the local currency. Hopefully someone will be able to confirm.

luci

Thank you Luci x

When I booked my trip for next year, I was told also it was in local currency

The departure tax can be paid in sterling or pesos. You can no longer pay in US$.

thanks denny. I thought it could be paid in dollars so its good to know