This is the first area of the game, and your first chance to make some major decisions for yourself. The enemies you will find in this area are entirely wild animals, and most of them are passive unless attacked, even at nighttime. This makes it a good, safe starting area- within reason.
Immediately, you’re faced with an interesting choice- do you progress the events of the game, or do you run around collecting items and smacking monsters?
Both options are good, for different reasons.
First of all, you’re here with Shulk and Reyn. As soon as you enter Colony 9, you’re going to lose Reyn from your party temporarily, which will make fighting any of the more powerful animals almost impossible thanks to Shulk’s relative frailty. That makes this an excellent opportunity to gain some early levels.
On the other hand, all of the creatures in the area relate to quests you can get in Colony 9. If you go around killing things before you enter the colony, then you’re just going to have to do it all over again once you’ve gathered all the quests in Colony 9.
Neither choice is definitively better than the other- but it is a choice you’re going to make, so it’s better to make it intentionally rather than accidentally.
Fortunately, the area you started in is a Landmark, so you don’t have to worry about losing a fight too much. From there, you will find yourself crossing through a rocky tunnel and down a narrow slope to a grassy area. Be careful, because if you leave the narrow area and enter the grassy field, you will immediately jump to Colony 9 and Reyn will part ways with you, pointing out that he needs to get back to work. You can come back out here fairly easily- there's a simple bridge between the field and Colony 9. If you like, you can head immediately into the Colony, or you can head downhill from the bridge and experience the lake and lakeshore. You can also head off the other way along a mountainside path that leads to stairs- these go up to a small park. If you were to double back on your original path for entering, you would see another mountain 'road' next to it that leads the other way- this will bring you to Tephra Hill and the Tephra Caves- but you don't want to go there just yet. It's a much more dangerous area (particularly the Cave) and besides, you haven't even looked into the Colony!
All of this area, and all of the lake on this side of Colony 9 or to the left of Colony 9 is fairly safe- even at night, the only creatures in the area that will attack you on sight are the Cute Brog, a kind of giant mutant frog. You’re probably not ready to handle them either, yet, so keeping it daytime if you’re on the lakeshore can be important. Most of the animals in this area range from level 1 near the Colony 9 bridge to level 7-9 if you reach the far West end of the lake or the bits of Northern lakeshore that aren't very far East.
Just be careful- if you climb up on Air Battery 3 just past Colony 9, there is a large level 18 bird-creature there that you’re not ready for- and worse, if you cross to the far side of the lake you will start seeing creatures in the 25-40 level range, which you definitely aren’t ready to handle. Some of the animals on that side of the lake -are- aggressive, too, so stay on your side of the water.
The Colony 9 area is also the first area in your Collection Book, so be sure to start grabbing those little blue lights.