I pay RD$1,000 for the trip from SDQ airport to downtown. My house is further than the Embassy, so you should be able to get the same price. If I do not have pesos I withdraw pesos from the bank of ATM's just to the right as I exit customs.
I usually will go upstairs via the escalator and ask one of the taxistas up there to get me a cab. I find they are easier to negotiate with than the ones downstairs, where the majority of the people get a cab.
If you pay in US$ you will pay $35.