To check if you will be able to survive in an area, highlight a monster in that area and select it and a menu should apear, clcik on check and the text at the bottom of your screen should read one of the phrases below.

Too weak to be worthwhile - this means the creature will be very weak and you will gain no EXP from it.

Easy prey - This means you should be able to tackle and defeat the monster quite easily, it's best to pick off this monsters while soloing.

Even match - This means you and the creature are the same level you never know if you'll beat it, it's really down to your skills, job etc. The EXP may be worth the battle.

Tough - This means the creature will most probably beat you not worth soloing.

Very tough - Don't attempt this unless you're with a party.

Incredibly tough - This could mean the monster has a good thirty levels on you maybe less maybe more, you can't tell. Either way this is a bad idea even in a party.

Impossible to gauge - Unknown, of course you can look on the internet for levels of these monsters. Monsters that have this are called NMs (Notorious monsters) they usually drop rare and valuable goods.

That is to the best of my knowledge all of the different phrases that can appear, maybe there are others, I don't know I only played till level 21.