光广东话
I'm thinking about learning Cantonese. Since learning Chinese is my primary goal, and since I don't want to overload myself too much, I would like to learn Cantonese to (for now) become fluent in basic conversation. I've been told that even though Cantonese officially has 9 tones, only six of them are actually used. Is this true? What is the point of having 9 tones if only six of them are used? I also understand that the grammar is very similar to Mandarin, but Cantonese has a much more evolving system of slang. Also, for any Mandarin students and speakers out there, what were your experiences learning Cantonese along with Chinese. Is it easy since you already know Mandarin, the mother tongue of Cantonese, or is it hard? What are your suggestions.

Also: Is anyone aware of a microsoft IME that I can download to type in Cantonese?

Question

光广东话
I'm thinking about learning Cantonese. Since learning Chinese is my primary goal, and since I don't want to overload myself too much, I would like to learn Cantonese to (for now) become fluent in basic conversation. I've been told that even though Cantonese officially has 9 tones, only six of them are actually used. Is this true? What is the point of having 9 tones if only six of them are used? I also understand that the grammar is very similar to Mandarin, but Cantonese has a much more evolving system of slang. Also, for any Mandarin students and speakers out there, what were your experiences learning Cantonese along with Chinese. Is it easy since you already know Mandarin, the mother tongue of Cantonese, or is it hard? What are your suggestions.

Also: Is anyone aware of a microsoft IME that I can download to type in Cantonese?

Answer

1. If you don't have a Mandarin background, it is not easy to master Cantonese, especially the speaking part. So u may needa put extra effort to reach this goal.
2. Cantonese has 9 tones. True.
    Only six are used? Not really. But majority of characters do have only 6 tones.
   What about the remaining three tones? They are for characters with ending consonants -t, -p, -   k. And these characters are very common in use too.
3. Is the grammar similar? Sort of, but definitely more complicated than Mandarin.
4. Slangs. There is a rich collection in both languages. But as a Cantonese speaker, of coz I do like cantonese ones more.

Answer

I think Mandarin and Cantonese have a big difference. The pronunciation.Mandarin can tell  how to spell ,Cantonese can't. my suggest is listening and talking .  talk to someone who can translate it for you .

Answer

I usually use some IMEs downloaded by myself instead of using Microsoft's, such as Quick(速成). But if u r not so familiar with Chinese characters, u can use pinyin instead, like SogouInput, which u can also use to type Cantonese. 
And yea, having a background of Mandarin is really good for u to learn Cantonese, especially in grammar learning. But on the other hand, it also has some bad influence on your pronunciation, since mandarin only have 4 tones but cantonese have 9, people speaking mandarin usually find it difficult to pronunce the additional ones.