The Garmin Edge series are excellent cycling computers and are dismissed by many GPS retailers as training aids. They can be used to very good effect to Navigate pre programmed Routes of up to 100 waypoints.
The learning curve with a Garmin Edge is very steep and you have not bought a device that offers the features of similar priced mapping or routing devices.
To simplify things for the Garmin Edge community I have written this simple Route Planning Tutorial.
If you do a Google search for "Garmin Edge 305", I'm on the first page with a link to my non commercial site.
This uses free Google Maps based websites to plan your Routes. Riding a pre programmed Route on a Garmin Edge is a very rewarding experience as you don't have to refer to a map or a route sheet.
Hope this has been of some help.