Mav,
I've been there twice, both times June 21-29th. It's a blast and I know that the bigger fish are taken around the end of may because in the airport there's sure some nice monsters in the low 70's on the wall around Memorial Day. We had a ton of fun, especially fishing out around sitka point for both salmon and halibut. We also did real well at sp. chezalov bay?? That was out of sitka sound and north a ways but don't get caught out there in a wind storm it's not much fun, let me tell ya.... Not in a open 23' alumaweld with a dory front end... Took on lots of water.. We stayed at Mertz Island and rented our own boats, it was all around a ton of fun and in the last week of june it's not uncommon to have 40-50 fish days if you want to fish that hard for them.. But after about 6 days the hands sure get to hurting from all the small cuts and saltwater infections.
Make sure to take some hydrogen peroxide and soak you hands every night in it for at least 5 minutes then wrap your small wounds with neosporin and bandaids.. It's a must if you don't want your hands turning into claws...
Hope that helps...
Keith