"Their whole family's great," says the Aussie actor, 20, who's been dating his The Last Song costar, 17, since August. "They've always been super friendly to me and very welcoming."
Does he consider the Cyruses his second family, especially since his parents live in Australia while he's been working in the States?
"Yeah ... pretty much," Hemsworth told PEOPLE Wednesday after surprising the Boys & Girls Club with a private screening of The Last Song at the ArcLight in Hollywood. "I love their family. Her parents are great [and] they're very friendly people."
As for Miley herself, "she's got such a big heart and [is] just so open," he says. Filming with her was a breeze – even though their first kiss was in front of cameras – since "we always got along really well," he says.
Adds Hemsworth, "We feel very strongly about each other."
Reporting by NINA TYLER
Get a sneak peek of this week's issue – Sandra Bullock's divorce dilemma, new Jolie-Pitt twin photos and more – which is on newsstands Friday