A hands on way of circulating the anti-invasion message may be stamping or writing on US currency. This method has been used by various groups over time and is an effective way to move your message hand to hand.

An explanation of the legality first.
"Won't I get into trouble for writing on my money?"
This is, by far, the most commonly asked question and the answer is...

Not unless you're making them "unfit for recirculation" and, according to Title 18, Section 333 of the United States Code, this is defined as "mutilating, cutting, disfiguring, perforating, uniting or cementing together, or doing anything else to a bank bill with the intent to render such item(s) unfit to be reissued". So, if you're only writing or stamping a message such as "No amnesty! Deport Illegal Aliens!" in NEAT lettering along one edge of the bill, you're certainly not making it "unfit for recirculation"!

Reproduction or alteration of currency with an intent to defraud does violate federal statutes; but using the greenback as a bulletin board for social protest does not. Article 331, Title 18 of the U.S. Code prohibits defacement of currency only if it is performed with such deceptive intent, or the depicted face value of the currency is altered in a significant way. How effective the tactic is remains to be seen. Would government suddenly take notice if hundreds of thousands or millions of bills were altered?

Here are some sample messages.
"This is a PATRIOT dollar"
"Vote for Amnesty and WE will vote YOU out!"
"Illegal Immigrants are Illegal, not Immigrants"
"Americans welcome LEGAL immigrants"
Or make up your own slogans to print or stamp.