Your Map can show you what squares that they are in.
Since you do not appear to be aware of that year old feature then I'll explain it.

Open your Map.
Click the Show Active Quests button.
Hover your Mouse over the name of whatever particular Quest you want to 'locate'.
The squares that can be satisfied in will highlight.

But be aware that Quest Names will be colore dRed if they are on a different Map, and that some quests, like Lucas, will not even show up since they can be done everywhere.