Hi Cathy,
We have spoken to our agents over in Mexico, who have recommended that a lunch will cost approximately 15US$ and a dinner will cost approximately 20US$. You will have to bear in mind the type of restaurant/café that you wish to eat in as the cost can vary.
As for spending money, hopefully someone who has been there before could give you a guide - we don't want to give you a completely wrong figure.
Kindest regards,
Monty