I need to raise the levels of my group in order to do certain quests such as getting 20 spores. However, the easy areas such as rat caves and beach were cleared out by me. Do these areas repopulate?

No they never do. There are wandering enemies and after you made a short work of them that's it, get your bonus XP and look for grinding elsewhere. Actually you're not supposed to fight in the forest, some of the mobs there will decimate you without breaking a sweat. You should pass through it to Sorrentia to meet with a hermit. To do so you will need to see enemies' zones of influence (it's shown when you hover the mouse cursor over an enemy in question). You will still need to defeat lonely Rasmaga (or something like that) to get to Sorrentia.

For easy XP kill Velegarn's guards, by which I mean=> if you're lvl 2-3, bless yourself with 4 stats,1 def/evasion and +10PP boosts and relieve them from their extorting misery. It will take something like 300 gold for 6 blessings, and remember you're paying for satisfaction you won't forget soon.