the MA programs at Bard and CCA both focus on contemporary art (CCA's visual/critical studies program might be an especially conducive place to tackle a project on street art culture):
Bard: http://www.bgc.bard.edu/programs/graduate-degree-programs/ma-program.html
CCA: http://www.cca.edu/academics/graduate/visual-critical-studies
also, though, i wouldn't rule out programs that don't focus explicitly on contemporary art... teaching at the community college level, you'll likely be asked to teach survey/intro classes... so taking a breadth of coursework might serve you well. and almost every top MA program has at least one or two faculty in contemporary art/visual studies who would be able to support your interests (ondine chavoya at williams, for example - http://latino-studies.williams.edu/profile/ochavoya/).
the upshot: in addition to looking at programs as a whole, look at the research interests of the individual faculty members who teach and advise MA papers in the programs.
good luck!