Written Arabic. A quick question?

I couldn't sleep the other night, so I learned to read Arabic instead. I speak it, but never got around to learning to read it. Anyway...I was looking on Google maps earlier and noticed, when reading the names of towns and cities in Egypt that there were none of the marks representing the short vowels. Is this merely a limitation of a computer font? Or are they usually left out? If so, are there rules to determine the missing vowel based on the surrounding consonants? Or -- and I'm hoping this isn't the case -- are people taught to read and write with them in place at first, but then they are dropped and the student must rely on recognizing the word to fill in the missing vowels?