No one actively cheats but the main couple do experiance relationship strain as he’s (unwillingly) spending more time with another woman than her. It is implyed other characters suspect him of cheating
There are lots of camera angles where they pan up slowly from the feet, all the way to the head of Sharpay Evans, who is always in heels and has her legs exposed in 90% of her outfits, including bikinis. The way it is filmed gives a more checking out of the character vibe. Some of the male characters often drool over her.