Several considerations to keep in mind:
- Do you need maps? The Edge 500 & 510 do not accept maps. They will show you a track on a blank screen. For most of the time, you can follow the track without problems. There may be times at an intersection where it is not clear which road to take. Never worry though. As soon as you are off the track, the unit will warn you.
- What do you expect your primary use of the unit beyond this trip? For regular bicycle touring & riding on new routes, consider the Edge Touring. It comes with maps for the region you bought it from. You can then download & add more maps for Puerto Rico. More discussion about that is at:
- What is your price limit? Go all out & purchase the latest Edge 1000, which promises great connectivity functions, clear screen, & maps.
- Do you want a multi-purpose GPS? For other uses, such as hiking & paddling, consider the eTrex 30. This is a solid unit, allows for many functions beyond just the bicycle, such as 2,000 waypoints to mark the route, man-over-board location marker, etc. The two AA batteries will last several days & you can replace them on the road. You will have to add the maps per instructions above.