Just because nobody has replied with a definite, I will give you this.
We just returned from a stay at CBR and there were 4 or 5 large containers with life jackets of various sizes at each pool.
We also had ADRs at the Grand Floridian and Beach Club. While walking around both of those resorts, I also saw containers with life jackets.
So of the 3 resorts we were at, all 3 had life jackets available at the pools. I hope this helps.