If the rest of the world reacts to “The Peanut Butter Falcon” the way Salt Lake City audiences have, filmmakers Tyler Nilson and Mike Schwartz will be delighted.

“Oh, my gosh, the audiences in this town,” Schwartz said this week, during a publicity tour for the warm-hearted road-trip movie that opens in Salt Lake City and a few other markets Friday and nationwide on Aug. 23.

Nilson and Schwartz marveled at the enthusiasm of the audience at an advance screening Tuesday night at the Megaplex at Jordan Commons. After the show, the filmmakers fielded questions for 45 minutes, and signed posters after that.

“There were these three kids, 14-, 15-year-olds,” Nilson said. “They were asking these really deep movie questions — like 14-year-old cinephiles. ... They hung out [after the Q&A], and we sat for, like, 30 minutes. We were, like, ‘Let’s start a podcast right now.’ The kid pulled out his iPhone and we did a live podcast.” The kids posted the audio on YouTube the next day.

“That’s not how people are in L.A.,” Schwartz said.

The response has been gratifying for the two first-time feature filmmakers, who have been laboring for five years to turn their unusual premise — fronted by the most unlikely but most charismatic of leading men — into a finished film.

It all started, Nilson said, with Zack Gottsagen, a young actor with Down syndrome. Nilson and Schwartz encountered Gottsagen when they were doing volunteer work, and saw a short film the actor had appeared in.

“It was pretty standout,” Nilson said.

The three had dinner, and Gottsagen told them he had studied acting in high school, taught theater at his local Jewish community center, and worked as an usher in a movie theater so he could watch the performances on the big screen.

Gottsagen also told them his dream: “I want to be a movie star.”

Nilson said he and Schwartz weren’t sure it could happen. “It’s not something I’ve ever seen done,” Nilson said. “I’ve never seen somebody make a film with a lead who has Down syndrome. And [Zack] was, like, ‘How about we just do it together?’”

Schwartz said, “He was such a magnetic character and personality that we were like, ‘This is the best possible thing we could do.’ It wasn’t charity.”

“He had earned it,” Nilson said. “We knew he had the chops. We had to build a dance floor for him to dance on.”

The filmmakers spent a year writing the script for “The Peanut Butter Falcon,” which centers on Gottsagen’s character, Zak, a young man with no family, living in a nursing home as a ward of the state of North Carolina. His dream is to learn to be a professional wrestler from his hero, a wrestler known as the Salt Water Redneck (Thomas Haden Church). The story is a road trip, with Zak pairing up with Tyler (Shia LaBeouf), a down-and-out crab fisherman on the run from rival crab men. And Zak’s social worker, Eleanor (Dakota Johnson), comes along for the ride.

Gottsagen, Schwartz said, “really helped us shape that character. When a character works, authenticity is a big part of it. And he had hopes, dreams, aspirations, but also frustrations. He was a well-rounded human being.”

The pair hit the road with Gottsagen, Nilson said, “really committed to learning the nuances of who he is as a human, and trying to put that in a script.”

Getting producers to read that script was a challenge, one that wasn’t solved until Nilson and Schwartz made a five-minute concept video that showed Gottsagen’s acting and the look they wanted to use for the film.

The video got the attention of producers Albert Berger and Ron Yerxa, the team behind such indie hits as “Little Miss Sunshine” and “Nebraska.” They signed on, and flagged the script to LaBeouf, with whom they had worked on another indie, “Charlie Countryman.”

The filmmakers expected LaBeouf to say “no,” so they were surprised when the actor contacted them via FaceTime from Finland. “He was, like, ‘I’m getting on a plane right now,’” Nilson recalled. LaBeouf had watched the video and skimmed the first few pages of the script, and told them, “I’m in. Do you guys want to do this with me?”

(Right after shooting “The Peanut Butter Falcon,” LaBeouf entered rehab, where he, as part of his therapy, wrote the script for “Honey Boy,” in which LaBeouf plays his own father, an alcoholic rodeo clown. That movie premiered at this year’s Sundance Film Festival and was bought by Amazon Studios, which will release it in November.)

Nilson and Schwartz, backed by their distributor, Roadside Attractions, are now trying to figure out how to market an offbeat family film. Opening “The Peanut Butter Falcon” in Salt Lake City is part of that.

“[This movie is] about family and love,” Schwartz said. “I don’t think the movie-star thing works any more. It’s about stories, and what do people want to feel. Salt Lake has a reputation for being really strong with family audiences.”

Nilson said he and Schwartz were surprised, as they were editing the movie, how the movie turned out. “I looked at Mike and said, ‘Oh my God, did we make a family film?’” Nilson said. “It’s the most gritty, hard-edged family film possible. … This comes from love, this comes from us, we really put a lot of heart in it. And we’re just hoping the world is ready to digest it.”