During a brief conversation with a couple of other parents this AM, I realized that I just wasn't sure when the pool actually opened. I thought it was the first week in July, but it's actually THIS weekend. Don't forget that the pools have pretty strict rules about what you can wear/bring with you.
If the weather cooperates, and if this year is anything like last year, you may want to avoid the first few days if you are bringing little ones. The AM session is a lot less crowded than the PM session. And after a week or so, if you get there right at 11 AM, you have 30-45 minutes before it starts getting active.
from the NYC website:
All 54 Parks outdoor pools have closed for the season and will reopen on June 27, 2009. Indoor pools remain open year-round. General hours of operation are 11:00 a.m. to 3:00 p.m., and 4:00 p.m. to 7:00 p.m. Call individual pools for more specific information.