$700 isn't much for a week. If you are a lonely traveller then you will be drinking a lot, in the casino and using hookers, getting drunk and ending up with a whore whether capable or not, drunk and whoring seem to come hand in hand (PI).
If you're all inclusive and with the wife then more than enough. If I was going to Sosua without the wife I'd make sure I had at least RD5-6,000 per day and extra for drunken escapades which always seem to cost a lot of money.
vacation always costs more than resident living so take that into consideration.
Best advice, never befriend a Dominican, ignore drugs entirely no matter how drunk, don't even mention words associated with drugs, someone somehow somewhere will have you locked up and extorted.