I am trying to learn Japanese with Rosetta Stone for a vacation in Japan. Is it important to learn all the Kanji or are there always Furigana?
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You say you're just going on vacation in Japan. Well, in that case, you might not need to know a whole lot of kanji. In fact, people go to Japan without knowing the language at all and manage to get around okay! So for your purposes, you might be fine without learning any kanji at all.
But what if you're trying to learn the language for real?
The fact is, there aren't always furigana.
Unless if you want to be illiterate, you'll need to be able to read words and names written with a number of kanji. How many? 2500 is probably a good number, although educated native speakers can certainly read more than that. It's hard to come up with an exact figure, but the number is definitely much greater than zero! Even if you can only read a few hundred kanji, you'll be significantly better off.
"Learning a kanji" isn't a well-defined task, though. What does it mean? Being able to recognize that the kanji exists? Being able to write it from memory? Being able to rattle off a list of readings associated with the kanji? Probably the most useful skill is being able to read words written with a kanji, but there isn't a fixed list of words for each character (although the jōyō kanji chart does list a number of examples).
Regardless of how you define it, you can't learn "all the kanji". Very large kanji dictionaries have upwards of 50,000 characters! However, you'll never see that many actually used. I have a character dictionary with only 8,000 characters, and even that is far more than I need to know. 4200 characters brings you to the 99.9% level, but many of those are names or other things which are likely to have furigana when they're introduced, so the real number you need to know is lower than that.
If I were you, I'd just learn kanji as you learn vocabulary. There's a lot more words in daily use than there are kanji, so before long you'll you know most of the kanji you need to know, and you'll find that the real problem is developing a large enough vocabulary. What's more, kanji actually help you break down vocabulary logically and understand words you don't know yet.
So do you need to know lots of kanji? In order to be literate, yes. To go on vacation in Japan? Probably not, but it couldn't hurt to learn some basics.