And yes, they talked about the team's tumultuous year.
"We went through it all," Stanton said with a chuckle Wednesday.
Shortly after their get-together, Guillen was fired as manager. Then in November, the Marlins reshuffled the roster and pared their payroll by trading five players to Toronto.
Stanton tweeted that he was angry about the deal, then went silent on the subject. Now one of the team's few established players, he's eligible for arbitration in 2014 and was the topic of trade rumors over the winter.
He has yet to discuss his future in Miami with the South Florida media, and said he won't until Friday, when the Marlins hold their first full-squad workout.
However, he was willing to talk about another aspect of the offseason — his 2½-week vacation with pitcher Ricky Nolasco. Besides Madrid, they traveled to Paris, London, Amsterdam and Barcelona, all first-time visits for Stanton.
In Madrid they got together with Guillen, who often vacations in Spain.
"We went to a soccer game with him, and we went to dinner and hung out in the daytime a little bit," Stanton said. "Everyone knows him there. He goes there every year. At his favorite dinner spot and stuff, they all were cool to us."
But through the entire trip, the 6-foot-5 Stanton said, not one person recognized him, even though he has hit 93 home runs in his first three seasons with the Marlins. He's by far their most popular player, and he'll compete in next month's World Baseball Classic for Team USA.
But MLB and the NFL aren't a big deal in Europe, he discovered.
"Going to eat and everything, it's soccer, soccer, soccer, soccer," he said. "I had no idea what was going on with American sports at all."
He and Nolasco went to soccer games in Madrid and Barcelona.
"You always hear about that stuff, but it's cool to be able to experience it live," Stanton said. "Watching it on TV doesn't do justice to how crazy it is in the stadium."
In Paris, the two Marlins took an evening boat tour on the Seine, and Stanton posted a photo on Twitter showing him in front of the illuminated Eiffel Tower.
"I didn't know it lit up every hour," he said.
Stanton said Madrid was probably his favorite stop, although he and Nolasco missed the bullfights because of a scheduling mix-up.
"We've got to go back," he said.
First there's a season to play. While Stanton may be unhappy about the Marlins' direction, he showed up several days early for spring training and has been taking batting practice daily — always a treat for spectators.
They included new manager Mike Redmond, who's new to watching Stanton's tape-measure blows.
"I watched him hit, and I know we lost a lot of balls out there," Redmond said. "I think of Bonds or McGwire. I don't think I've seen a ball jump off a bat like that since watching those guys play. That's why everybody talks about him the way they do. He's special."