We booked at the 11 month mark but then switched at the 7 mo. mark. We were waitlisted for BW SV for one day before our request came through (Jun. 10-12). Then we stayed at SSR for the next two days - no waitlist.
No swimming while at BWV but the pool did not look overly crowded. SSR's pool was busy, but I would not label it crowded. The Grandstand pool was not really busy at all and is a nice pool.
As far as heat, it was horrendous our first two days -well into the 90s - then turned lovely with temps in the mid 80s the rest of the week. Yes, there were daily storms that ended within an hour, but were violent nevertheless.
All in all, I think June is probably the best of the summer months to go.
Enjoy!