We usually change £ for $us in order to tip, however some people obviously tip in £ as we have helped out staff in the past by changing £1 x 20 into £20 notes that they can then change at the bank. :uk1:
We tend to tip a lot, both because the staff deserve it and because we feel like it's a good way to do a little "charitable giving". Some friends of ours took a bus ride through the actual city of Cancun (not the tourist zone), and saw where a few of the TTR staff people live (they knew, because the staff were on the bus and got off at their houses). The houses were pretty small and run down. They're definitely not living large off our tips, and they typically have families to support. So ,given to the advantages we Americans and Canadians have compared to Mexicans, I don't mind helping out some good, honest, hard working folks by tipping a little more than I normally would.