Be aware when you are approached by someone on a motorbike or bicycle and this person offers you a free tour. This guys usually will tell you that they just want to practice their English so they will offer you a free tour. Avoid these people at all cost. There is no free lunch. At the end of the tour, this guide will ask you for money. If you don't pay them can get rude and aggressive and drop you really far away from the point where you start. So you will always waste money to back to your starting point. There are no free tours!