NOT all Edge units do routing! The newest model - the Edge 500 - will not accept waypoints or routes. it is still a great bike computer, but it will not work for you so scratch that one.

Also, you DO NOT need maps. Maps are nice, but not required. For a car GPS I would say maps are needed - but not really for a bicycle. Here is what you can do even if your GPS will not display maps.

1. Get the coordinates for your start point, end point, and each turn. Mapmyride makes this easy, once you are a registered user you can download routes in either garmin format or GPX. Simply transfer the route to your GPS and that is it. You may not have a street level map, but you have an ordered collection of waypoints that creates a route. The GPS tells you how far to the next nearest waypoint in the route, as well as which direction to turn.

2. Assuming you are not using map my ride, no problem. You can still get coordinates for intersections off Google Maps. Then you can use Easy GPS (a free download) to easily upload the waypoints into your GPS. After that, create a route and you are done.

Sure, full maps are easier - but NOT really "needed". I did plenty of marine navigation (as in no street signs, no roads, but plenty of fun things like shallow areas, submerged objects, and whatnot) using a GPS that had no charts (maps). No depth contours either. I used a paper chart to pull the coordinates, ordered them so I avoided hazards, then put them into the GPS and created routes. It can be done.

And by the way - even the top of the line 705 does NOT come from the factory with street level maps. It will have a base map which will show the major roads - but those will likely be roads you avoid anyway (unless you like riding on interstate highways). You will have to buy the street level maps for an extra $150 or so. Without the additional (and optional) map detail your 705 will still require user supplied waypoints / routes or else it is just a 500 with a color screen.

My 305 will allow me to enter 100 waypoints (which is a lot - way more than I need for any one ride unless it has an insane amount of turns) and store up to 50 routes (so long as the 50 routes do not contain more than 100 waypoints total).

Using a computer program I can store unlimited waypoints / routes amd just upload what I need for each ride to the GPS.

Bottom line is that routing is VERY effective and easy to use with any of the Garmin units EXCEPT the 500 which WILL NOT store waypoints or routes.