I've lived in Miami all my life, and the one thing that I would say is that you probably need a car to get around. Unless you want to do Uber/Lyft or carpool. If you live on/near FIU, then I think you should be good because there is a Publix, Walgreens, etc. right across the street from campus. However, it would mean having to carry your groceries. I was lucky enough to live only a few minutes away from FIU and even though I didn't have a car, I relied on Uber/Lyft, parents, friends, etc. to drive me to and from campus and to wherever else I wanted/needed to go. One of the reasons I'm moving away from Miami and even Florida for my PhD is because I want to be more close to things, and since I'm not planning on buying a car, I would need to do things by walking/biking. I also want to have a change of scenery and environment (people, culture, etc.). Many people who think of Miami think of the beach. I'm about an hour away from Miami Beach. It's beautiful there. I don't think Sweetwater is that nice surrounding FIU, but it just depends where you go. Miami could mean Sweetwater, Brickell, Coral Gables, Kendall, etc. There are certain places that are nice and certain places that are just run down and not so pleasant.
These are just my personal opinions after living 20+ years in Miami, FL.