Basically, you will either see english or Kanji numbers depending on the type of product, sign, place, etc. In Japan, you will usually see romanized digits (usually written horizontaly) on "newer" things. For example, you will rarely (if ever) see something at a 7/11 that has Kanji numbers instead of romanized numbers. In addition, Japanese people will usually use romanized numbers when listing prices, labeling items, etc. Generally, the only time you will see Kanji numbers is at older places (like temples for example) and at traditional, fancy restaurants (usually used to list the prices of meals or on their signs).