I would say it really depends on your abilities and your compatibility with your instructor. If you find someone that you can really connect with, you will surely have a much better chance of absorbing the information presented to you. On the other hand, if you can't fully understand them because of language differences, or any of the other many reasons it could prove to be difficult.

In my opinion, I would sign up for one class and go from there. If you like what you get for your money, by all means go for the rest of your classes. It surely would suck big time if you spent a bunch of money for 3 classes only to find out that you are unable to learn what they are trying to teach.

Just my 2 cents.