Just going off the top of my head - you may want to check me on this, but:
Red Road Commons I believe start at about 1600 per month for a 1/1. Merrick Park is closer to 2000 per month for a 1/1.
There are certainly some cheaper options, but just be careful. Coral Gables itself is very safe, but I have a few friends who rent houses just to the west of campus, and they've been burglarized, and in one case, a victim of an armed robbery. Not to scare anybody, but be careful and definitely scout out the neighborhood before you move in.
Also worth noting - a popular option for a few law school students I know are apartments on Brickell. Brickell Ave. is one of the nicer areas in Miami, located right next to downtown. It's literally a stones throw away from the Heat arena, and the performing arts center, and most buildings have water views. They constructed a lot of new condominiums before the housing fallout, and as a result, there are a lot of vacancies/lower rent. You can find a nice 1/1 on Brickell with a water view for +/- 1600-1700. There's a metro stop located on Brickell, and the line runs right down to Campus in Coral Gables - assuming you won't have a car/don't want to battle rush hour. Definitely an option if you want to experience the Miami "High Life"
Hope I didn't inundate you with too much info -- I should probably go into Real Estate instead of Law haha