ET breaks news: Britney runs for the border.

BRITNEY SPEARS was just spotted at Rosarito beach in Mexico.

As of last night, she and ADNAN GHALIB -- paparazzi photographer turned rumored romantic interest -- are tucked away in Baja.

The Internet has been abuzz with speculation as to her whereabouts, with rumors flying that she took off to New York after reports surfaced that she boarded a private plane yesterday.