"On the plane -- L.A. here we come!" Montag posted on Twitter. "Home, sweet, home."
Montag admitted she was "so sad to leave Mexico," but "ready to get out of pig flu country!"
On Tuesday, Pratt told Ryan Seacrest that they're "definitely wearing facemasks everywhere.
"I'm not playing -- I'm not trying to get pig flu," he added. "We're in isolation, we're in full hiding."
Montag and Pratt wed in front of Hills pals Audrina Patridge, Brody Jenner and Lauren Conrad Saturday.
"I can't believe I'm married!!!!!!!!" Montag tweeted. "So soooo excited -- Mrs. Pratt!"
Up next for the couple: their honeymoon!
"I'm ready for a honeymoon!!!" Montag wrote. "Done with my music video...best one yet! Get ready."
The couple is discussing "going to Tahiti or Fiji, somewhere tropical and exciting," Pratt said yesterday.
When asked if MTV is footing the bill, Pratt replied: "We'll see. Since it is a recession, we might just be going to Santa Monica Beach!"