Right now the RAT shows availability for a 1 BR at DHHIR for late April and all of May. Even though there are just 18 1 BRs at the resort, a front desk CM told me that sometimes a 2 BR is harder to get than a 1 BR. That's because the resort seems to attract families, often extended families, who tend to go for the 2 BRs. I remember sitting near the front desk one day, listening to a family who wanted to extend their stay. The front desk explained that there was availability for a 1 BR, but not a 2 BR.
I don't know about September, but I just read elsewhere from someone who just got a 1 BR with only a month's notice for October!