I hate amusement parks. But the Wizarding World of Harry Potter is so much more than a theme park. It's a visit to Hogwarts, Hogsmeade Village, and Diagon Alley, plus a ride (or several) on the Hogwarts Express. I recently spent two days in the park. And the level of thought and detail that went into planning it all out is just staggering. Except for the crowds, you really feel like you're there.
This place has something for everyone. Those who love the thrills and chills of roller coasters and other rides will have plenty to keep them happy, even if they are muggles who don't know a garden gnome from a house-elf. Those of us who get sick on rides but love all things Harry Potter can ride only the Hogwarts Express and spend the rest of our time immersing ourselves in our favorite magical world. Even if you don't want to ride, be sure to go through the lines to see the interiors of such attractions as Hogwarts Castle and Gringotts Bank; the staff will let you walk through without riding.
And be sure to eat in the park. You will not find theme-park staples like greasy pizza, funnel cakes, or Coca-Cola in the Wizarding World. All the food and drink served here would be found at Hogwarts, Hogsmeade, or Diagon Alley. You can get delicious butterbeer, though unfortunately, it's all nonalcoholic, like in the movies (for very good reasons, of course, but in the books it contained alcohol); pumpkin juice; pumpkin pasties (so good!); all kinds of candies described in the book as coming from Honeydukes, the snack cart on the train, or the Weasley twins' joke shop; and British staples like fish & chips and shepherd's pie. If you have a picky eater in your family - as I do - who must have standard American theme-park food, many other parts of the Universal Studios and Islands of Adventures Parks serve it. (Jurassic Park, for example, is only a three-minute walk from Hogwarts and will gladly serve you pizza and burgers.)
When I visited in late June, the crowds were large but manageable. The longest I waited in line for anything (the Hogwarts Express) was 45 minutes, and most were less than 20 minutes. You can beat the lines by staying at a Universal property (we were at Cabana Bay), which allows you into the park an hour before general admission opens, so you can see the most popular attractions before the crowds get thick. Universal also offers an express pass for skipping the lines, but you can't use it on some of the most popular Harry Potter attractions, so check the find print first to be sure it's going to be worth the expense.
Speaking of expense, most theme parks have all kinds of shops and concessions whose purpose is to make you spend even more money there. The Wizarding World does too. The difference is that here, the shops and concessions are part of the attraction. In the books and films, Harry and his friends spend quite a bit of time shopping in Diagon Alley and eating at Hogsmeade Village. So you won't get food at a generic food place here; you'll eat at the Three Broomsticks or buy candy at Honeydukes. If you want a souvenir wand to take home, you can get one at Ollivanders, the same shop where Harry bought his. Yes, all of this can run into a lot of money, but it is all part of the fun. And you can just go to Ollivanders to see the free demonstration of how a wand chooses the wizard; nobody will pressure you to buy a wand or anything else.
If you do want a wand, there are interactive ones on sale at Ollivanders and several other places in the park. They cost around $50 -- about $10 more than the standard, non-interactive wands. And you can use them to cast spells in different stations throughout the park, where you stand on a special symbol on the pavement and wave your wand at what's in front of you; for instance, to make an oversized book in a store window open up. It didn't seem worth the extra money to me, but my son (age 14) really wanted one, so I gave in, and he thought it was great fun. You might think so too. I would suggest not buying one immediately. Walk around a bit first, watch other people using the interactive wands, see what the lines are like at the stations where they can be used (most had no lines at all, or short ones, the day I was there) and decide if you think you'd get a kick out of casting spells that way.
If you want to see both parts of the park (Hogsmeade and Hogwarts are in one part and Diagon Alley is in the other) you will need to pay for a Park-to-Park pass. You cannot ride the Hogwarts Express without one! Of course, it's more expensive this way, but unless you're planning to come back often, it's completely worth it. Also, this gives you admission to the other attractions at Universal Studios and Universal Islands of Adventure. So if you don't want to spend all of your time at the Wizarding World (you Muggle!) you'll also be able to see what's at Toon Lagoon, Jurassic Park, KrustyLand (Simpson's-themed), and more. I spent two days pretty much at just the Harry Potter locations, but my husband and son enjoyed KrustyLand and a Popeye-themed water ride, too.
The staff is helpful and friendly, even those who are wearing thick velvet wizarding wear on a 95-degree day. They're all dressed as if they've just stepped out of the books, and are happy to talk to you about their characters. And be sure to catch them in the free shows. We saw a performance by a small group of singers from the Hogwarts choir, with bullfrogs, and also sat down to watch a dramatized tale from Beedle the Bard, with puppets. Wonderful!
You'll have a magical time.