Look in the upper part of the screen to find the current threat level, which changes every minute, depending on the level of the players on the same area:
If you are alone in the area, nothing happens. But if some player gets near you, the threat level may go up to level things. If it's a player of similar level than yours, then it's ok. But if it's a high level player (4000-5000), then the threat level will go up much more, to keep things balanced.
The higher the threat level is, the harder the enemies, and the more damage they can do to you.
For someone of your level, any place in which the threat level is more than 3 may be too dangerous.
On a side note, the Mount Tam area is the starter area of the game. As such, the threat level is always lower there and can't go past 3, i think. So if you go outside of Mount Tam, you take the risk of going into an area in which the threat level is too high, maybe because there are high level players fighting there, or maybe because a high level player just happens to pass near you.