I am going to weigh in on this one.
As an instructor, of course I am biased, but here's why.
Putzing around in a sunfish on a warm inland lake is an awesome way to learn how to sail, and those of us who learned to sail this way, often encourage others to do so.
But if you're planning on going sailing in the Gulf islands, at very least, get out there with some experienced sailors first of all. We have some of the fastest tidal passes anywhere, due to the incredible amount of volume of water entering and exiting the Georgia Straight twice a day. Our water looks beautiful and calm, but we get some challenging conditions, and they can evolve pretty quickly. Planning on sailing up to Skookumchuck Narrows? The current there runs at over 15 kts at max flood, and I've seen videos of huge tugs being overturned. You have a 5 minute window there at slack tide to safely make that passage. Care to play roulette with your boat and your life, or does a lesson make sense?
Not sure where the shipping lanes are, and what the rules of the road are?
"Geez, I'm sailing, doesn't that give me priority over the freighter that's bearing down on me at 35 kts?" Not if you're in a commercial shipping lane, it doesn't.
Our water temps in the Straight mean that if you wind up overboard, whether in winter or in mid summer, you're into severe hypothermia in 40 minutes; the kind where they airlift you to the hospital if you're lucky enough to have your hand-held with you when you hit the drink.
If you don't believe me, pick up a cheap VHF handheld, and monitor channel 16 on a busy long weekend. You'll get a quick education in how many things can go wrong, really quickly. And most of the people calling in their 'May-Day's' are 'experienced boaters'. I don't mean to sound heavy-handed, by I interrupt my own sailing holidays quite a bit to help out boaters who are out there figuring it out on their own. Hitting a shoal while sailing at 8 knots though, may cost you your boat.
No, formal instruction will not stop you from making mistakes, and you need to make a whole bunch of your own. Only not sailing will prevent that. But formal lessons will point out in advance, a whole pile of classic blunders that can be very expensive. You don't need 'a bazillion courses and get a million certifications before you leave the marina', but some on the water instruction is a pretty good idea. If you don't want to get formal lessons, definitely spend some time on the water with experienced skippers. If you do decide to take on-the-water courses, then choose them based on the kind of sailing you plan on doing. If you plan on cruising, take a cruising course. If you plan on racing, follow that track. But the cost of a 4-day sailing trip with a professional instructor is less than my annual haul-out and bottom paint, or a couple of month's moorage.
And in the winter, why not take a coastal navigation course and the VHF radio operator's course? Cheap courses and money well spent. The cheapest insurance is the knowledge of how NOT to wreck your boat. Boats and everything on them are expensive; lessons are cheap. I was a self-taught sailor, and in the process of going through a whole series of courses, was shocked at how many knowledge gaps I had. Anyhow, that's my 2 cents worth.
I'm pondering how high a priority I should put on finding instruction (not necessarily formal lessons, more likely just sailing with experienced skippers).
I'm no stranger to boats, and can happily sail around aimlessly (I can even lay a course with set and drift, which is more than some). I've never raced, and have no idea how to bend a mast to change the shape of a sail.
Would I be a fool to pick a light day and go tack around? Should I carefully wait until I've spent more time on boats of a similar size? Should I take a bazillion courses and get a million certifications before I leave the marina? I really feel like I should d*mn well just go and make my own mistakes, but I still have enough rational thought left to question this foolish idea.
How great a store do you set by whatever CYA/AYA courses or racing as compared to old fashioned learning?