I am going to Playa del Carmen in Mexico in April. Will it be cheaper to change GBP into US dollars or pesos?

I went to Playa Del Carmen 2 years ago. I basically took Pesos for my daily spending and US dollars in case of emergency thinking they are more familiar with US currency never the less they take any convertible world currency there. I would avoid exchanging in local shops though. There is a HSBC bank right in down town Playa so you could exchange your money if you need it.