Lots of new students of the Japanese language manage to rely too much on Romaji (or English alphabet) to get by when they are studying or figuring out Japanese. This is primarily because whenever we begin studying Japanese, we want to jump right in and learn how to speak the language. Just learning Hiragana or Katakana can take precious time, and after you really can't even recognize much (you can read, yes, but fully grasp...no)..
Fine, so what's the problem? You're still studying Japanese, correct?:
Sounding Like a Foreigner
You are currently accustomed to saying things a particular way while you're reading Roman characters. Japanese characters, however are fresh to you and you do not have to worry about this. You are starting with a blank canvas here and you will learn to pronounce Japanese phrases accurately without being negatively led astray by your present relationship with the English language.
Japanese People Really Don't Use Romaji
Perhaps your Japanese book uses Romaji. It is still no excuse. That means that it was produced by a lazy publisher. Truth be told, you will not really find much Romaji being used when you go to Japan. Maybe just the names of major department stores and certain English words here and there. If you write something down in Romaji and give it to a Japanese pal of yours, he or she will most likely be pretty lost because quite frankly, Japanese people more often than not, just don't use Romaji.
Today's Shortcut is Tomorrow's Liability
If you feel you will want to keep studying Japanese and eventually become really good at it or even get proficient, you'll need to learn Japanese characters sooner or later. It's only going to be less difficult to learn them from the get-go. An inch of effort now or a mile of anguish later on. Which might you rather have?
Sure, so Romaji is not the most effective way to go. What should you do if you are just starting out? It honestly depends upon what kind of Japanese student you are. From my point of view, there are 2 types of Japanese students:
The Dedicated Person
Maybe you are majoring in Japanese at school. Maybe you're considering traveling to Japan for a while and need to get ready for your stay. Maybe you're a business person that has many Japanese customers. Or maybe you simply have a lot of Japanese pals and you're sick and tired of them talking about you behind your back.
If this represents you, the most effective step you can take is to sit down and learn Hiragana and Katakana. These are definitely quite simple to master and by taking it a little at a time and progressing at your own speed, you can possibly master them in one or two weeks by using some flash-cards. Following this, you can proceed and work at establishing your vocabulary, sentence structure along with other speaking skills using Hiragana and Katakana as a good foundation.
The Hobbyist
Maybe you are traveling to Japan for a few weeks of family vacation. Maybe you truly like manga and would like to learn more about the culture. Maybe you merely love learning languages and want to try your hand at Japanese.
If this looks more like you, then I'd advise that you start out by simply understanding some simple conversational Japanese. This is often less difficult than learning how to read and write, primarily if you're immersed in a good quality program. Once you've got some simple conversational Japanese down, it could be that you would plan to take it further and honestly learn the language completely. Going forward you will end up in the ideal place to take the path listed above and master all the Japanese symbols (including all those bothersome Kanji).
So I trust you can fully grasp now why depending on Romaji really just isn't beneficial for you. Regardless of what your eventual goals are with learning Japanese, you will be far better off if you spend your effort and leave the crutch behind and either study Hiragana and Katakana or practice a little conversational Japanese.