Misguided teenage pranks, or gang signs?

These tags appeared on a wall next to the Riverwalk off Calvary Street in Waltham sometime last year. They were still there as of this morning. The person who did it, "Chino" or "Chano", obviously has some artistic talent. Too bad his talent has to manifest itself through this type of activity.

What really bothers me is not the destruction of someone's property (the wall is part of a building that houses a heavy equipment rental agency) or the vandalism to a great community resource (the Riverwalk). It's the message conveyed by the words "Mexican Power" (in the first picture, to the right of the clown's face). Being proud of your ethnic or national background is one thing; asserting that background with words that suggest militancy at others' expense is another. It's no different than "Black Power", "White Power," etc., in my mind.

There's another disturbing possibility as well: the tags could be the calling cards of some local gang marking its territory or announcing its presence. Just last week I saw a similar "Mexican Power" tag on the sidewalk next to the playground at Lowell and Chestnut, with the number "13" added below it, and a skull next to it. When I saw that number, I instantly thought of MS13 ("Mara Salvatrucha"), a terrifying El Salvadoran gang which has been responsible for violence in Somerville and East Boston. Are the "Mexican Power" and "13" tags a sign that the gang has set up shop in Waltham, or allied itself with another immigrant gang with Mexican roots? Or is it just some local kids searching for/asserting their identity, using terms designed to intimidate?