I highly recommended you try the bike before buying, but that isn't always possible. The one bike I have purchased without seeing was a little small for me. It still fit me though, and I probably could have made a few more adjustments than I did to get an even better fit. Now that I own a number of bikes, I have a much better idea of what will and what won't fit me.

A good bike shop will help you get the right size and a proper fit on any bike.