There are so many institutions (Almost all big universities) in BJ that offer Chinese language courses.I guess the one with the most foreign students is Beijing Language and Culture University.However,when there are too many foreigners,you may be getting lazy to practice your Chinese.
The best way is to contact the International Education College or Foreign Affairs Office of a university in your neighborhood.
I am a recruiter in TUTCM in Tianjin,which is another option for you.