Dungeons and dragons online

Hello I heard alot of good things about dungeon and dragons online but I have still a few questions.
Before I will download the game I want those questions answered so if you can answer them please do.
Okay so I wanna know if you just go out of town will there be monsters to train on? Or do you have to go through portals and stuff like that to train?
Or are only the dungeons behind portals.
And if you run out side of the town will you often see other players or is it like your playing alone?

So please answer these questions for me if you can.
Thanks
Iwantlvl99