No, conversations are pretty much out for me. I am notoriously bad at languages. Any foreign language I do manage to pick up is invariably on the reading not verbal end of things. I just like to know pronunciation and how to read a train timetable and possibly how to read enough "food" to order something I'm expecting to see.
I'm a bit concerned about navigating the postal service, I'll admit-- that was a total nightmare in Italy.
The reason I have a different answer than other respondents, might be I've traveled to some less common parts of Japan. Most American tourists do: Nikko, Tokyo, Kamakura, Hakone, Kyoto, Osaka, Nara, Himeji, Hiroshima and Miyajima. Some also try; Sapporo, Okinawa, Mt. Koya, Fukuoka, and Nagasaki. the places I'm thinking of where there is noticeably less English are places like Zao onsen, Towadako, Osorezan, and Tsuroka. In general, to make up for that, people I've met in many of these places were incredibly friendly and kind even though I didn't always know what they were saying.
Most Limited Express/Shinkansen trains will have boards telling you the name of the train and its stops in English. You might just have to wait because it cycles through several options. If you have a smart phone, you can also use Google Maps or Hyperdia to chart trains. Most of the time you just need to know the station you want to go to. There is a lot of English, but sometimes you need to just wait for it to cycle through. Buses can be harder, but I've seen some of them are putting out more schedules in English. Bus stops are less likely to have English so know where you need to go and listen for it. Some buses are quite nice and have more than enough space for luggage and some are tight and compact.
If you are going in July 2017, it would behoove you to book hotels now, things will book up. I've only been in August and a few days of July in Japan, it's hot and humid, but if you can survive other hot and humid places you will be fine. The biggest difference is unlike Houston or Orlando, the Japanese don't tend to over air condition things.
Tokyo Disney is crowded. Stay as close as you can afford because you want to be there as early as possible. The Japanese are quite good at getting to things early and waiting patiently in line. The doll events I've attended in Japan generally start at 10, but many people are there by 7.
If you stick to the post offices in bigger cities most of them are quite good at helping foreigners both with packages and buying stamps. I've mailed a LOT of packages from Japan. If you're mailing packages, make sure it isn't just cheaper to buy another suitcase and bring stuff home that way. I once paid $10 to United for an extra box, it would have cost me a lot more to send the same box to myself. Stamps are fairly obvious, especially if you bring in the postcards already filled out. There is a way to send postal money orders in Japan, and I have done it, but that was a little more complicated. In general, people are happy to help.
If you're not a picky eater and willing to eat nearly anything, food won't be an issue. Some places have English menus, and many places have food models. (You can even visit the city they are made and make them yourself it turns out!) Food models tend to be a popular souvenir.
I wouldn't worry too much, my first trip I went alone and managed and I think I knew maybe 3 or 4 words of Japanese.