I contacted Garmin customer service and they told me "Your nuvi 255 does not support multiple point routing. As such, it will not be possible to transfer a route from your computer to the device. I apologize for any inconvenience."
It does have a slot for a micro SD card, and I was thinking I could download mapsource and use it from the card, but if the nuvi won't support it, I don't want to waste the money.
