I also have this problem. Let me explain a little further because it can be a little tricky to understand this.
In the regular US Mac keyboard there are keys we, portuguese speakers (and a lot of other), use to make the words like: ` " and so on. But Apple didn't do a keyboard for us like they do for french speakers, so we have to use the US standard keyboard. In fact it's not a big deal, the keyboard is almost exactly the same as ours. What changes is the behavior of these keys.
For us, the system "waits" for a key to be pressed after these special signs. So if I press ~ the system will wait until I press another key... if I press a key that can combine with that sign, the system joins them as a whole symbol. In this example, if I press ~ then a it will output ã. Quotes are also special because they do a sign we use in letter u (so u + " = ü)...
It is a thing about the keyboard and the OS, not exclusive with OSX or Macs. Windows does that too if you are using an US keyboard trying to write in portuguese. So I guess there are a lot of users with this very same problem.
EDIT: putting quotes into context