"Have a good time" or "Have fun" are common ways to say "祝你玩得开心" in English. Both phrases are used as a way to wish someone enjoyment or pleasure during an activity or event.

Here are some examples:

"I hope you have a good time at the party tonight." (我希望你今晚参加聚会玩得开心。)

"Have fun on your date tonight!" (今晚约会玩得开心！)

"Have a good time" and "Have fun" are both colloquial phrases, which means they are commonly used in everyday conversation, but are not considered formal or polite language. If you want to use a more formal or polite way to say "祝你玩得开心," you could use a phrase like "I wish you an enjoyable time" or "I hope you have a pleasant experience."