If you ask about rules when driving...rules don't exist. The only rule is don't stop, don't be polite and only come in to trafic. Driving licence take with you.
Cash or credit/debit cards? In supermarkets, restaurants you can pay by card. In smaller shops, souvenir shops it is better to have cash money. Don't let anybody to leave with your card! Specialy at petrol staion. In Punta Cana you can pay with USD or Dominican pesos. 1USD - 50 pesos. You can change money in close pharmacy at petrol station.With ATM you can have troubles...Dominicans twice a mont get salary and after that ATM are empty!
There is several beaches around. "Our" beach is Bibijagua. There you have sun bes for free. Close beaches are: Cortecito, Los Corales. Macao Beach is about 20 minutes far, Bayahibe beach is about 1 hour away. Thanks to scooter which we provide (or rented car), you can visit all of them.