Are you talking about WPB campus or Ft. lauderdale campus?
First of all, tri-rail does not go as far north as WPB campus. It stops in Mangonia park which is by 45th street and congress. That is about 10 miles south of the WPB campus, which is by PGA Boulevard three exits north on I-95.
As far as the fort lauderdale / davie campus. You would have to take another bus from the airport tri-rail stop. This is very inconvenient. I would say if you cannot afford a car, then you have to live right near the campus.
For WPB campus, you absolutely must have a car. It is one satellite building near a very residential area, and the Gardens Mall, and I-95.
The problem with tri-rail is:
it is only good for going downtown Miami, and a few other places.
It spans 72 miles (Mangonia Park to Kendall), including metrorail when you get into Miami, but is really only one line, if you consider that and metro-rail.
If it is WPB campus, I think you have to move there from Miami. It is simply too long of a commute.
If Fort Lauderdale, you can easily just drive there from Miami.