Divirtámonos
Pasémonosla / pasémonoslo bien
Vamos a divertirnos
Divirtámonos vamos a divertirnos
lets have fun mate
Vamos a tener.
nomas
there is not an exact translation for it; it depends on what you want to say. ex: lets go eat - vamos a comer lets jump- saltemos ( as you can see in this case there is no word used instead of lets, but it is understood as lets jump)
I have fun with you: Me divierto contigo.
It will be fun - será diversión
Te has disfrutado = Did you have fun
divertir
Vamos a jugar!
If Mexican is just Spanish then have fun! is : ¡diviértase!