As of 2011 there were 448 foreign language immersion programs in the US across 38 states. Source: Directory of Foreign Language Immersion Programs in U.S. Center for Applied Linguistics, 2011
Here is what is available in the Washington DC Area.
In Washington DC, there are a number of dual language programs. Historically most of these programs were created to benefit hispanic/latino english learner students. With the advent of research showing the benefits of these programs on all students, other programs, addressed to all students, were created.
Currently, all but four of these dual language programs are in NW DC, and none of them are East of the Anacostia river.