Regarding chair and loungers rentals - 7 peso would not even be a penny Cdn unless the exchange rate changed drastically since March/05!
We used the ATM twice in the 2 weeks we were there and the first time we got 1,822 pesos per $1. Cdn and the next week, we got just over 1,900.
If you went 1,500 to the $1 Cdn, 750 pesos would be $0.50 Cdn, 375 would be $0.25 and 75 pesos would cost you $0.05 Cdn.... not much!!
I agree with you about leaving anything on the beach - we took turns swiming. The Capilla (where we stayed) did have a "roped" off area for their hotel guests with free chairs, tables and towels along with a security guard.... The Caribe does not have that.