Well, start with one then do the other. You don't need a complete knowledge of Mandarin. You need the vocab and grammar (and most of that is similar to Cantonese) and you need the pronunciations of the characters mostly used for transcriptions (and you don't need this until you're pretty advanced in reading). I had it easy, as I already knew Mandarin when I started with Cantonese. There are a lot of places you could start learning. My advice would be to begin with spoken Cantonese and forget all about the writing until you have a basic command of the language. There are studies that indicate this is the more effective way to go with Sinitic languages. Learn Cantonese with Jyutping or Yale transcriptions. As you get more comfortable, picking up signs and learning some reading and Mandarin / Standard Written Chinese vocab will come gradually. The two most important rules in language learning are:Quote
bullio
So I should learn both languages at the same time? :O
How should I do this? :|
1: Spend time trying to learn the language.
2: Don't stop.
I speak enough languages to consider myself speaking from experience here. There are better and worse methods (avoid Rosetta Stone like the plague), but in the end the factor that outweighs all the others is how many hours you're putting in. And how interested you are. If you're motivated and keep putting in the hours, you'll get there eventually. Just be aware that there will be plateuas where you seem to be going nowhere or even backwards, but keep pushing and you'll improve.