We've always had lifejackets available for use at all the resorts we've stayed at. We've brought pool toys, baby float seats, balls etc to use and never had a problem. We also always leave them or pass them on for others to use during their stay as well. No sense in packing them again.
Also, all the water parks also offer life jackets for use as well. On our last trip we saw a couple take a life jacket from the resort to Typhoon Lagoon.

I believe it is the intention of the resorts to have the life jackets stay at the pool and not for them to be brought back to your room or to other parks!! We saw some of this happening for the first time at CBR this year. I was quite surprised that some people thought it was their oportunity to just keep the jackets for personal use throught their stay.
But, not much surprises me anymore when it comes to people.
