Bill D, you may be right that the enforcement of the law may be put on hold until all constitutional challenges have made their way through the court system. (I'm not confident that the same 5 SCOTUS justices who just overturned 100 years of precedent, plus the original intent of the Constitution, to allow unlimited campaign contributions from coporations will not somehow find a contorted argument for ruling this obscene law constitutional.)   
But some of this kind of harassment and persecution has already been going on, even before Brewer signed this law into effect. And it will probably get worse now that this law is on the books, even if it's challenged in court.

There may be situations in which "profiling" is warranted - e.g., if a robbery suspect is described as a tall white male with a beard, you look for people who kind of fit that description, not for short black women.    But even if the majority of illegal aliens in Arizona are from Mexico, that does not imply that even a large percentage of "Mexicans," much less of all "Hispanics," are illegal.    Targeting most "Hispanics" because most illegals are "Hispanic" is badly designed profiling - the kind that persecutes innocent people without really helping deal with crime.

Before a law like Arizona's would be fair or sensible, better, clearer criteria need to be established for what constitutes probable cause to suspect someone is illegal.   Not speaking English could be a component of such a profile but neither a sufficient nor a necessary one.    Being paid cash "under the table" for very sub-standard wages might be another component (in which case probably the employer needs to be investigated) too.
But I can't see why anyone who is minding his or her business and not violating any other laws should be stopped and required to prove they have legal resident status, except in the case of businesses suspected of hiring illegals so they can exploit workers.