IPUMS CPS provides data from the Current Population Survey, which is a monthly U.S. household survey conducted jointly by the U.S. Census Bureau and the Bureau of Labor Statistics. Therefore, if you are looking for information on people who live in South and/or Central America, you will want to look into data available through IPUMS International.
BPL indicates whether persons were born in the United States and, if not, the foreign country where they were born. So, if you are interested in people who live in the U.S. (at the time of the survey) but were born in South or Central America, then you can use the codes that fall under each to identify those individuals. A “n.s.” after a label is indicative of “not stated”, in other words, someone who is from Central America, but did not specify which country in Central America.