Dating or summer fling? Zac Efron Michelle Rodriguez may not have branded their relationship yet but they are still having a good time together.

Zac was spotted leaving Michelle's house in Los Angeles with his overnight bag in tow, after an overnighter following a night out with pals on Saturday at Chateau Marmont. Zac was also carry carrying a skateboard when he left.

According to sources, Zac and Michelle were having some fun hanging out in the back garden of the West Hollywood hot spot with a group that included Robert Pattinson.

Michelle just go back from from New York, where she spent her 36th birthday last week with other friends. They partied at Mister H in the Mondrian SoHo and according to source she acted "very single" during her time in the Big Apple.

Michelle seems to be just having a good time, which may include her supposed relationship with Zac. She shared an Instagram video of herself chowing down on a chocolate cake with a candle stuck in it, captioning the funny clip, "Thanks for the Hotel BDay Chocolate fix I'm skipping lunch today lol ;)"

A source close to the couple confirm rumors that the two are just having a "summer fling." "They aren't dating per se, but I'm sure once they see each other again they might be all over each other again," the source added.

Meanwhile, Zac was playing house at Michelle's as he spent Thursday through Sunday there. Though he was not alone and some friends were seen coming and going, at one point Michelle left for work during the week and Zac he stayed put.

"Michelle is super-cool and laid-back and Zac has always been attracted to her because of that," a source said earlier. "She's one of those people that everyone likes, she just gets on with all kinds of people and doesn't take the fame thing too seriously."

"Zac likes the fact that she is laid-back and he can relate to her," the source continued. "He is attracted to her great attitude. They understand one another."