Yeah, you can get them all season but it can be spotty and thin some summer nights. Springtime they move into the harbors around the spawn. IMO the first half of May is the peak time to get them in the harbors. Also gets pretty good in the fall. (But still spring seems better IMO)Squid only live like a year or year and a half. They all die in about a month after they spawn. When they die they sink to the bottom. Hence if you are a fish, it is pretty normal to see a dead squid in the bottom in June or July.
If you can get fresh local squid in the supermarket that is great. Many times what you get is squid from CA that has been "washed" (all the ink and sometimes the internals removed) I would not buy this unless you plan to eat it yourself. Like mikeP said, fresh local is the ticket, you will see a difference in the attraction to this bait.
If it is a pain for you to get them yourself, talk your tackle shop dealer into purchasing a few totes of fresh from a dragger. Some shops do this and call them "ink squid" or local ink squid and sell them frozen in a box or bag to differentiate them from the boxed CA washed stuff.
Squid juice tends to make my hands itch a little, esp on a hot day while working for fluke.

Don't get it in your eyes either.
