Walmart in Homestead no longer allows overnight parking and even with security guards it was kind of dicey. We only stayed once.
We do, however, stay regularly at the Miccosukkee Casino (at the corner of 41 and 997. We always take the slow route down and avoid 95/Miami area as it is just too busy for our liking...cutting inland at Hobe Sound (76, 98, 27, 997). Just our preference.
We also check gas prices along the way with gasbuddy. Last year we found that gas pricing in the upper keys (at one station) was cheaper than along 997 (which was not typical).
Enjoy your trip.
Flying J's can be quite noisy so we have yet to stay at one of them. Rest areas along 95 would be our choice...many walmarts along that route are saying no to overnights (argh).
enjoy your trip