When you get ready to purchase the good stuff, visit as many shops as possilbe. Try finding a size that fits. emember, different brands can vary in size eventhough the numbers are the same. Some have different methods of measuring the frames. Ask online for a fit calculator (road forum). Compare online and actual data to one another. This will give you a pretty good idea of size before you spend the dough!
Note: Some of the better shops will find the correct size them swap components free of charge to make the bike even more comfy for you. I've bought bikes that were the correct size but just a little too much of a reach. They swapped the stem for another shorter stem free of charge.
Entry level bikes are still good as grocery/cruiser bikes. But not for the dirt trail where you need full control.
