Charlize Theron and Sean Penn jetted to Mexico for Valentine's Day.

The couple, who got together late last year, were spotted boarding a private jet in Cabo San Lucas on Monday (17.02.14) after flying there on Friday (14.02.14) for a romantic long-weekend without the South African's two-year-old son, Jackson.

A source told E! News that the 38-year-old actress and 53-year-old actor stayed for three nights in an oceanfront suite at the five-star Las Ventanas al Paraiso resort, where they ''had a romantic candlelit dinner by the beach'' on Friday night.

The Oscar-winning stars ''had a personal butler, [but] didn't ask for too many things and kept to themselves.''

The insider added they were ''very low-key and spent most of their time in their room.

''They swam in their private infinity pool together and took a nap in a hammock under a palapa [aka Tiki hut]. (It) was a romantic trip for the two of them. They definitely seemed to want privacy, and just to be alone together.''

But the 'Prometheus' actress did make time for a yoga class during their trip, while Sean was seen lifting weights in the hotel's gym.

The couple, who celebrated New Year's Eve in Hawaii together on December 31, flew back to Los Angeles on Monday.

A source previously revealed that the 'Milk' actor and Charlize are already talking about getting married and recently moved in together.