Hi. I'm a newbie. I'd like to write about the level of Japanese needed to travel in japan. I hope my advice will be helpful.
It seems to me that the most important thing is to show that you are willing to use Japanese.
If you try to communicate in Japanese, people respect your attitude to speak Japanese and listen to you carefully. As they listen to you speak Japanese, they understand how good your Japanese is, and adjust to your pace. When you cannot catch or understand what they say, you could repeat exactly what you caught. Then, they will repeat or rephrase to explain what you cannot understand.
In addition, they perhaps try to use English, or just pronounce English words they know. Please listen to their English if it is comprehensive, which will be helpful to get information or understand what they say.
Since you know some Japanese and have enthusiasm to speak it, your stay in Japan will be successful.
Please don't worry too much about your Japanese skills. Just let them know that you can speak Japanese saying "Konnichiha" or "Sumimasen."
Break the ice and have a nice trip