Issues with disruptive tenants in college condo and neighbors

[James Call]

My wife and I own a condo in a college town in Utah.  

We have 4 women renting the condo.  Two are students and two are non-students who work in the area. 

One of the non-students and one of the students are roommates and share a room. The other student and non-student have their own private rooms. The non-students are close friends and the students are both close friends.

One of the "non-students" just called to ask how to get out of her contract.  She told us that the students are bringing over guests starting at 10pm and staying until the wee hours of the morning.  They are making a lot of noise and don't allow her to sleep. 

She also told us that one of the student's male friends makes her feel very uncomfortable with vulgar language. 

To add a monkey wrench in the works, the men who live in the next door condo are smoking pot.  She has called the cops on them and it hasn't accomplished much.  We had a previous tenant who also called the police on the next door neighbors for smoking pot. 

We DO NOT want to lose the non-student as a tenant.  Our contract says something boilerplate about tenants can't disrupt the peace of other tenants. 

What should we do about the noise and the annoying visitor?

Do we have a meeting with just the students and give them the "first warning"? Just verbally and tell them that we have mailed something to them?

Should we hire an attorney?

What about the pot-smoking neighbors?  It is still against the law in Utah to smoke pot, by the way. :)

Thanks,
James