Tampa parking lot for dry parking /boondock ?

In Tampa, Walmart 1575 Land O Lakes Blvd (US 41) Lutz FL. Check it out on Google Maps. 2 options: after a right at stop sign, take 1st right and park along edge. Or go to the opposite end near garden center.
Walmart between Tampa and Orlando: Lakeland FL 5800 Us Highway 98 N
Lakeland, FL 33809. I-4 exit 32 then left if going east.
I would let the manager know you are parked for the night and buy something in the store.
You can also check for Cracker Barrel Restaurants off I-4. There is one at exit 10 where the truck stops are. I would get there early as this is a very busy exit for RVers.
Florida Rest Areas allow only 3 hours parking. No overnight camping.

I-4 exit 10 there is a TA truck stop that has parking UP FRONT that can be used for overnight. Seen RVs there quite a few times.
Don

Most of the Cracker Barrels in Florida allow overnight parking.

Did you check Free Campgrounds and Free Campsites?

Boy you are covering quite a bit of area there and Tampa and Orlando are not exactly adjacent to each other.. If you could be a little more precise maybe we could help or check the Allstays website for maps that show WalMarts, rest areas etc.