First, look here
www.laughingplace.com/Guide-Cal-DLR2-200706.asp for hours and entertainment in June 2007. I went the last week of June 2007 as that fit our other schedules.
Grad nights go for the first few weeks. Grad Nights occured on evenings where DL closed at 9PM (e.g., June 7), which means reduced park hours, potentially reduced entertainment, and disruption of MM (aka EE) as DL does not do MM on the morning after a Grad Night.
1. First week of June was reduced entertainment and slightly reduced hours. School not out on SoCal. Grad Night on Thurs.
2. Second week was full hours and full entertainment, with the exception of Fantasmic which was in refurb until June 14. That will not happen again in 2008. Grad nights were on Wed and Thurs. Schools start to get out late this week or the following week.
3. Third week has full hours and entertainment. Grad Night on Thurs. All SoCal schools out by this week.
4. Fourth week is fully into summer operating mode. Full everything, with no Grad Nights. One issue that occurs this week are SoCal AP blackouts, which go into effect this week. This means all SoCal AP holders (which are the majority) get blocked out until late August. After the blockout the crowds reduce, but before the blockout the crowds increase as the AP holders squeeze in one last visit. This has been especiilay true the last couple Junes when AP holders have squeezed into to see the Nemo Subs (2007) and the POTC refurb (2006). I was there this week in 2008 and noticed the crowds drop noticably but not hugely before and after the blockout. See the 2008 blockout schedule here:
www.mouseplanet.com/misc.php?pg=blackout
If it was me and I could go during the second week with full hours and entertainment, plus SoCal schools not out yet, I would chose that week. But do not assume that will absolutely be the case. I seem to remember that in 2006 DLR did not begin summer operating hours until week #3 or 4.