Not all of them are RIBs.
My Zodiac has an inflatable keel, marine plywood floorslats, and I do, infact, pump it up by foot. Its not made from some cheap material though.
What differentiates a RIB from a boat like yours or is yours a RIB? From my time in the Navy, I guess I just classify any Zodiac type boat as a RIB. You wouldn't normally deflate it, just pull it around on a small trailer, right?
The one I am looking at has the plywood floor and the rigid motor mount. I only have a little 3 HP Evinrude but I figure for getting just off the beach a bit in Venice it should work just fine. Would you have reservations about leaving an unattended boat in that situation?
Up to you. Just make sure you use a good anchor if you leave it. I don't think anyone will bother it if you have a dive flag out. You'll need the bigger flag (20" x 20", I think) attached to the boat. I tried anchoring my kayak once with the folding fluke anchor that I had and I ended up chasing it quite a ways when the anchor folded up and began skipping across the sand.
It probably wouldn't be much worse than pulling a kayak along, which is what I do now. A plus is that you always surface right where it is, like dkramer said. One thing I've done is put a 5 foot length of bungie cord (buy it by the foot at ACE) in the anchor line because it will jerk you around a bit when the wind and the waves pick up.