All those lovely summer dresses that everyone seems to be wearing are about a foot too long on me in the XL sizes. I am 5'2" and usually wear XL or XXL and size 14-18 depending on the type of clothing. Where can I find summer dresses for short rounds?!
I also have trouble with fabrics, and I'm a bit short and very busty. Lots of things that don't bother others feel scratchy or itchy to me. I'm 5'4" and usually wear a 16W.
Here are the places I shop:
Dillards has a wide selection if you go to the largest store in your area. The smaller the Dillards, the smaller the selection. The stores that carry "bridge" usually also have a much larger plus section. They do carry a few items in plus-petite, which will be in the plus area, not the petite area. Remember that the petite items are not just shorter but a little smaller overall, so you'll want to go up a size. Dillard's also has the most comfortable capri cargo pant that I always wear to the parks. Always. It is a thin but durable cotton material that really breathes with just enough spandex to stretch a bit for comfort and a really comfortable stretch waist that is NOT gathered, so it lays flat all the way around, giving a much more flattering shape. These are the ONLY pants I wear in the park.
Wal-Mart: I was really surprised that I found anything at Wal-Mart that looked cute. My daughter kept telling me, and we had to swing by there for something specific (after probably a decade of boycotting that store), and I found several shirts.
Talbots is my most expensive option, but I swear they are worth every penny. I have sweat pants from there that are ten years old that still look new. Everything I buy there lasts and lasts. Their sizes are very consistent, so once you figure out what size you are, it's easy to buy from them. BE SURE YOU GO TO A PLUS STORE. They also have Petites in Plus sizes. You can go online and have things in the store put on hold for you so that when you get there you know things are ready for you to try on.
Lane Bryant is nice because you can order online, and they deliver to the store for free. I spend a ton of money upfront to try stuff on, and most of it gets refunded as soon as I try it on because I return so much of it. It's hit or miss, but it's worth the time, trouble, and upfront investment. They have lots of knee-length dresses that may work for you. Their long-length dresses are very long -- too long for me at 5'3". Honestly, I don't buy a lot of stuff there, but practically half of my daughter's wardrobe comes from there. WATCH FOR THEIR 40% OFF SALES -- seriously, they do flash sales for 40% off the entire store.
Macy's has a lot of clothes that look like they came from Wal-Mart but are at Dillard's prices. Make sure you go there when they are having a sale so that you get the best deals. And just look through everything to find the good stuff. They DO have good stuff, but you have to look.
Ross is tough for me because their merchandise is always changing. Everyone tells me if you go often, you'll find more stuff, but I don't have the time for that. A lot of their merchandise is for younger people, so depending on your age, you may find a lot. My daughter finds a lot there.
Kohl's is one of my favorites. Their pricing is amazing, and I always find something. Their cargo capris are not nearly as nicely made or comfortable as the ones at Dillards, but they are half the price when they are on sale (almost the same price when regular price). This is another store to make sure you go when they are having a big sale.
Old Navy has some nice tee shirts that are super soft, but you have to order plus sizes. They are having 30% off the entire store today. I've had good luck with their tee shirts, but I haven't ordered anything else because I don't want to deal with returns.
Eddie Bauer has XXL which fits me very nicely, but they don't carry a ton in that size in the smaller stores. I have to go to the big mall. I've never really seen dresses, but I get a lot of tee shirts from them.
That's all I can think of right now, but if I think of others, I'll post again.
Also, I am not sure where you are from, but the sun is a lot stronger in California than many other places across America, and in Florida, you really want fabrics that breathe. Take my advice and do not wear dark colors. Even when it is 50 degrees in the winter, the sun can really heat up a black pair of pants or shirt or even some shoes, especially if made of synthetic fabrics. And the synthetic fabrics just do not breathe, which will leave you feeling like you're wearing saran wrap in Florida. The best way to go is light to medium colors in breathable cotton (with some stretch added like spandex) for both Florida and California.
Out here on the West Coast Disneyland and Downtown Disney I have very rarely found a 3x, which runs small.
Yes, I figured you were talking about WDW, I was just saying how it is out here. It is probably the same whichever Disney place you will be going to. Larger sizes are usually a rare find. It is as if POOH people don't exist, UGH. 
