You might have to wait a month after your interview to receive your letter. I was interviewed on Jan 21st and still have not recieve a letter. People who were intervied on jan 14th just received their letter two weeks ago, and some of the people that were interviewed on Jan 22nd recieved their letter. I got frustrated when a friend of mine received his letter and I didn't, eventhough, we were interviewed at the same day. I emailed UOP and they said that they are behind with their decision process, but they did mention that they will send out all result of admission (jan 21st interview) by the end of next week. If you do the math, that is 2 1/2 months of wait.
My advise, DO NOT expect any letter from them soon.