Don't forget that some of them, like the three mentioned (Grand Biloxi, Casino Magic, Isle of Capri) plus Beau Rivage have a free shuttle between them (hop on hop off kind). IP and Boomtown may even be a (long) walk but walkable (as I remember).

You can also get a free shuttle from Grand/Biloxi to Grand/Gulfport (takes approx 30-40 minutes). They run pretty regularly.

If you have a car, its pretty easy to get to all of them. Most of them are straight up the street from one another.