It seems like against law to flying the Mexican flag on in USA's land without along with US flag.
Just check out this link...
http://www.senate.gov/reference/reso...df/RL30243.pdf
US Flag Laws and Regulations
Now, it's up to judge, plus vandal other country's flag seems not right but if people are remove the flag without vandal this flag would ok or so.
I just wonders if people are hanging the other country's flag (UK, Canada, Mexico) than US flag on their house's properties then would be ok?