How many ESL students are there in the US?

About 3.8 million.

In the 2003-2004 school year, there were 3.8 million students studying English as a second language (ESL) in the U.S. This is according to the U.S. National Center for Education Statistics. This number represents 11% of all students for the year. Among all U.S. states, California had the most number of ESL students with 1.6 million.