I think a GPS should be pretty high up on your needed safety gear list. They are so cheap now-a-days that if you can't afford it, you certainly can't afford drinks in Avalon. Even if you're a great navigator, nothing will save you faster than being able to communicate an accurate location to rescuers. Most days visibility can be pretty bad, and you'll spend most of your channel crossing not being able to see land at all.
Prevailing conditions would be the wind blowing from the island, so you'll be beating all the way there. A lot of locals leave early and motor over, and then sail back. The wind usually picks up in the afternoon, blowing 10-20 knots, with gusts to 25 knots. The swell is usually on your beam.
If you end up anchoring you'll need lots of ground tackle. The island falls off very steep. Being small you might get to squeeze in, but Avalon is always crowded.
It would be an easy sail to Laguna from Avalon.
A guy who races with our club sailed his Cal 20 from MDR to Isthmus, but that's a beam reach the whole way.
Also keep in mind you will be traversing shipping lanes.
I always go to the Isthmus, we usually motor across early. One time we got a late start and the wind was already blowing, and we made it across on one long beautiful tack. Our friends showed up later with wide eyes and said it was nasty out there, wind was right out of the island now.
Caribbean 50 Ketch