"They spent the afternoon lounging around and having drinks [at Jen and Justin's house]," an eyewitness told Us Weekly Dec. 27. "They seemed to all be really good friends and comfortable around each other. Emily was lying in John's lap, and Jen had her arms around Justin. They were there all afternoon until sunset, laughing and having great conversation."
Aniston, 43, and Theroux, 41, arrived in Mexico two days before Christmas. "Every day they followed the same routine, with a workout in the morning with Pilates and yoga, followed by tanning time all afternoon," a source tells Us. "All Jennifer wanted was to work out, tan, have margaritas and be with her man."