Amator, good for you! I don't know much about the bike you describe but the "one size fits all" raises a red flag. By far the most important thing about a bike is that it fits you and I doubt you can get a good fit by just raising or lowering the seat. If that's what your LBS is proposing, shop another place and keep shopping until you find one that will take the time to fit you properly, regardless of the price of the bike.
And let me recommend bike commuting. There are many folks on this forum who ride every day to work and they'll be happy to share their tips, tricks, and experiences.
Good luck and good riding!