I hope this isn't too late, but here it goes.

I've stayed at the LaQuinta near MIA before. It's in a decent neighborhood and had reasonable rates from what I remember. It's under the approach path for one of the east runways, which is cool. It's not too loud though which is nice.

If you have some free time, go check out El Dorado Furniture. I've never been inside the store, but right near the parking lot is a great spot to watch the freighters land and take off.