Yes for sure, monks also. They often joke in dharma talks.

The guideline on speech even for monks is to avoid harmful lies. Not to avoid humour and jokes :)..

And the basic guideline is to help others. If what you are doing is benefiting others then you are on the right lines. If you become grim and introverted and trying to control every aspect of your life to become a perfectly controlled person - you aren't helping anyone, just making yourself depressed.

There is a place for discipline. But for the most part it's to do with obvious things such as not stealing, lying etc. And then meditation to do with opening out  to others and your surroundings.

And there may be a place for more discipline including mindfulness, for instance to meditate is a discipline, you decide to set aside a certain amount of time to meditate - but that will depend on the teacher, how they teach that in your tradition. And Buddhists don't have to meditate. Many lay Buddhists never meditate (except in the West where of course they all do). It doesn't have to be central to your life as a Buddhist.

In some ways of meditating and following the path, then there is a lot of discipline, e..g the zen monasteries, some Therevadhan monks. Or you may even go and meditate in a cave for years, but you'll have guidance in that case on how to do it, which helps keep it balanced. It's never discipline as an end in itself. But part of a larger picture.

If you are not following a particular tradition or path, the main things to aspire towards are the five precepts, to avoid killing, especially murder (for most of us not a hard precept to keep), to avoid harmful lies, to avoid stealing that which belongs to others, to avoid  sexual misconduct (depends on your culture - if it hurts others) - and intoxicants at such levels that they could make you do any of the other things in a debauched drunken state.

Beyond that, well the discipline may come naturally as you follow the path. It can just arise out of the other practices you are doing.If you are acting with compassion, wisdom, wish to help others - loving kindness, then that by itself leads to the discipline that you need,. you naturally behave in a way appropriately to others. Which of course can include joking and fooling around, going to cinemas or whatever :).

And mindfulness in Buddhism doesn't at all mean tightly controlling every aspect of your life. Indeed the tendency to do that is in some ways our main problem. Its got a more subtle meaning which you gradually appreciate as you practice following the path.