At Which U.S. Consulate in Haiti the Interview Will Be Held
The U.S. currently has only one embassy in Haiti, which is located in Port au Prince and handles both immigrant and nonimmigrant visas.
You will be given instructions (and eventually, an appointment notice) when your case is transferred to the embassy in Port au Prince, and can also check the embassy's website for information.
If your spouse happens to be living in a different country, other than Haiti, the consulate there would likely be the one to handle the case.
Procedures If Your Spouse Is Already in the U.S.
If your spouse initially came to the U.S. on a nonimmigrant (such as on a fiancé, student, or tourist visa), and either you are a U.S. citizen or your spouse is still in valid status, he or she can apply to adjust status in the United States. The main form for this is an I-485. The two of you will attend an interview at one of USCIS's field offices.
Information about USCIS locations or service centers can be found at its website, www.uscis.gov.
Just be sure your spouse didn't commit visa fraud by using the nonimmigrant visa specifically to enter the U.S. and apply for a green card – see "Risks of Entering the U.S. as a Tourist, Then Applying for Marriage- Based Green Card" for details.)
If, however, your spouse entered the U.S. without inspection or by using a fake visa, or you are a permanent resident rather than a citizen, your situation is more complicated than this article can address. You may have difficulty obtaining a green card for your spouse, though it is not impossible. See an immigration attorney for details or if you have any questions about whether you qualify to adjust status.