If you’re mostly staying in cities, a year of WaniKani should be fine for reading signs and menus. If you can, try to get a little speaking practice in so that you can ask things like “Is my hotel in this direction?” and “Where’s the bathroom?”. Also, one of the most useful words in your travels will be “すみません”.
As mentioned by many others in the thread, signs tend to be in Japanese and English, so navigating most public transport is not too difficult even if you know no Japanese, especially in the cities. By the way, Google Maps is your friend. I highly recommend having a cellphone with some maps application because it really makes traveling around a lot easier.
For restaurants and menus, it really depends on the restaurant. I’ve been in many that were katakana heavy, and some that were heavy on the kanji. However, many of the restaurants I’ve been to have displays of some sort for the food. Menus tend to be picture heavy, and a lot of shops like having the plastic food on display. So, even if you have some troubles reading the menu, you can usually just point to what you want.
In general, people will try to help if it looks like you’re struggling. At one restaurant, one of the employees practically hurdled over the counter to help my friends and I use vending machine for the tickets to order our meals. At another, the waitresses brought out all the variations of their menu (they had it translated in Chinese and Korean) to try to help us with ordering.