There is a rack of life jackets at the pool. But I have seen it empty. And we have walked up to get one and didn't have one in my son's size. if you have the means to bring one with you I would.
There is always a couple kids with a foam football or water ball that are throwing it around but I don't think rafts and large pool toys are allowed since I never see them in the pool.
I guess that would depend on time of year. We go in Janaury and never had a shortage. They do have sizes xs - xl. Their xs fit our 2 yr old just fine on the first trip. Now our last trip their ages were 4 & 6 and had no issues with availability or size.