Hi, I was told I need my birth certificate in order to apply for temporary residency. I'll be in the sosua, El batey area in 3 weeks. Where is the immigration office located at. I has was also told I need a chest x-ray done. Please fill me in if I need to complete any additional requirements.

There isn't an immigration office in Sosua, only Santo Domingo, the capital.
Yes you will need get an x-ray, but again that is done in Santo Domingo.
There is a list of the other items you need at Dominican Lawyer

http://www.migracion.gov.do/res_provia.html

http://www.migracion.gov.do/res_provia.html

do yourself a favor, fork over $950 to this lawyer in Santo Domingo, and he will have your visa in 2 months. With his inside connections at the Migration Bureau, you will be ushered in and out in 45 minutes. All you need is copies of your passport and the standard photos for your new cedula, green card as it were. You can be eligible for the transitional visa after 45 days here, but if you wait, you will have to pay a few pesos on the tourist entry thing. Oh! It will cost another $3800 pesos on the day of the physical. This is a real deal because, like I wrote, all the other papers normally needed are unnecessary. It really is worth a day trip to Santo Domingo to get this done, quick and easy. write to attorney Jordi Blade at info@gotodr.net or call his office 809-616-1970 , cell # 809-350-0098 if you check around you will find that you cannot beat his prices or service, richard holden navarette