Slate's Today's papers says

Although McCain spent much of the primary campaign assuring Republicans that his priority in immigration policy would center on securing the border with Mexico, he's now singing a different tune. Mindful of the growing importance of the Latino vote in swing states, as well as the fact that Barack Obama has a strong lead with that group of voters, McCain is now espousing "a message that gives equal weight to helping employers and immigrant workers and their families," says the LAT. In new ads, McCain says that dealing with the needs of immigrants is "as important" as securing the border. Although he never comes out and says he wants to create a path to citizenship for illegal immigrants, "his subtle language matches that of legalization advocates," notes the LAT.

Obama, as a Democrat, is trying to convince the same Latino voters that he's a professional panderer:

McCain wasn't alone in trying to appeal to Latino voters yesterday. ("Como se dice 'pander' en Espa?±ol?" quips the Post's Dana Milbank.) Obama also addressed Latino voters yesterday and said they shouldn't believe the words coming out of McCain's mouth. "We need a president who isn't going to walk away from something as important as comprehensive reform when it becomes politically unpopular," Obama said.

Also in Slate, Mickey Kaus analyzes McCain's speech to LULAC:

First say "First": McCain's speech before the Latino Organization of the Day makes sure to include the word "first."

"Many Americans, with good cause, didn't believe us when we said we would secure our borders, and so we failed in our efforts. We must prove to them that we can and will secure our borders first, while respecting the dignity and rights of citizens and legal residents of the United States of America." [E.A.]

Byron York is impressed. I hate to be picky, but even if you think McCain actually believes his constantly-shifting formal position, the statement remains ambiguous. Is McCain saying he first must actually secure the borders or that he first must prove to the voters that he can secure the borders? I don't think it's crazy to believe the second interpretation is the correct one—or at least that McCain's drafters left it open to potentially give him wiggle room later (i.e., "We wouldn't be passing this historic comprehensive reform today, with the help of my Democratic friends, if we hadn't convinced the voters that we can and will secure the borders.")

No one should trust McCain.  Remember what Vanity Fair quoted him as saying:

Then he added, unable to help himself, ”By the way, I think the fence is least effective. But I’ll build the goddamned fence if they want it.”

What that means is he doesn't care—he's just going to tell voters what he thinks they want to hear.