Sorry-don't know the cross street.
As for jalencastros' question, you are better off calling the morning you plan to go to see about availability. I would not make reservations if you are not sure you will be able to make it.
I really don't think during the time you are going that getting a room will be a problem, but if you are in Santo Domingo there are a few places you can stay that are nice if the Casona Dorada is booked.
There is also the Hotel Pe?alba at the end of Calle El Conde right across the street from the church. Its' a nice hotel with a restaurant on the first floor that has an outdoor area perfect for people watching while you have your meal.